I have lived here for a decade using UK Tesco mobile phone number(s) for UK banking and other security verifications on a Pay As You Go basis (along with a Thai phone and bank here). It worked okay but it may be time to change,

 

I could top up over the phone using the tesco automated service numbers for top up responding to keyed entries for choice input (press 1for x/  2 for y etc) or via their tescomobile websites. The card I used had to be cancelled just as the tesco network seems to have been upgraded with keyed input choices (1 for x etc) no longer accepted. Inputting a different bank card to the topup website has so far failed the "Verified by Visa" service for MasterCard after the OTP had been successful. The bank helpline could see no impediment to payment so my current guess is that "Verified by Visa" may kick out a Thai IP address or fail from a wrong setting in my laptop. 

 

It didn't rain until it poured - my questions:

 

What is a better way to keep a UK phone number going for the very limited purpose of security verifications? It won't be used for much else. 

 

Has anyone have any insight on why a phone keypad might fail outbound to the UK system? 

Would there be an impediment or implication to using a Thai bank card on tescomobile?  I guess the longer you are here, the more on a Thai card, the better.

Is there any difference between banks or devices used in the "Verification by Visa" processes? I have set up HSBC cards successfully but am failing with a new NatWest card using an old laptop.  

 

Thanks in advance for advice & best wishes to you all,

 

KR

 

503

 

1 hour ago, 503726 said:

What is a better way to keep a UK phone number going for the very limited purpose of security verifications? It won't be used for much else. 

Subject has come up often and many have said they use the same system. Personally I use Asda and quite a few said they used Giff Gaff as they will, or used to, post out sim cards to Thailand.

Whichever you use the issue is still being able to top up. I think the last time I needed to was over 4 years ago (mainly just OTPs so free apart from 180 day keep alive SMS) so can't remember what I did, but I know in the distant past I used Skype to call CS and added a new card over the phone. Once the card was added to my account/phone number it wasn't an issue.

 

1 hour ago, 503726 said:

Has anyone have any insight on why a phone keypad might fail outbound to the UK system? 

Sometimes on a banks security call where I have to input or speak the numbers showing on my pc the keypad input does not register but no idea why that is.

 

1 hour ago, 503726 said:

but am failing with a new NatWest card using an old laptop.  

Do they have you with a Thai address and or have you tried to use a vpn to see if it makes any difference? 

Giffgaff. Worked for me just fine for over a decade.

Giffgaff works fine for me as well. You can port your Tesco Mobile number to their SIM. After activating it, you’ll be given a link to transfer your old number. You’ll just need your Porting Authorisation Code from Tesco Mobile.

 

You'll need to make a phone call or send an SMS with the SIM at least once every 6 months to keep it active.

 

https://www.giffgaff.com/

 

For anyone using an old 3G only phone upgrade is required

Virgin Media O2 3G Switch-Off: What It Means For Giffgaff, Tesco Mobile And Sky Mobile Users

The company aims to complete the nationwide switch-off by the end of 2025. While most users already rely on 4G or 5G-enabled devices and will see little change, those with older handsets could lose mobile data access unless they upgrade.

Impact on Giffgaff, Tesco Mobile and Sky Mobile

Giffgaff, Tesco Mobile and Sky Mobile are mobile virtual network operators (MVNOs), meaning they run their services on O2's infrastructure. As a result, their customers will experience the same loss of 3G access as O2 users once the signal is withdrawn in their area.

The most immediate impact will be the loss of mobile data for anyone still using older, 3G-only devices. Without 4G or 5G capability, those users will no longer be able to access the internet outside of Wi-Fi zones. Voice and text services are expected to continue over 2G in some locations, but performance may be weaker and coverage less reliable.

https://www.ibtimes.co.uk/virgin-media-o2-3g-switch-off-what-it-means-giffgaff-tesco-mobile-sky-mobile-users-1744225

Thanks all, I might give giff-gaff a go as a back up as tesco has become less friendly to use presumably through implications with the infrastructure carriers here & in the UK. 

 

I worried about the effect of 3G phase out so started a different Tesco pay-as-you-go SIM on a 5G phone. Today that phone would not recognise any keystrokes  to the auto top up service. Its Tesco card seems to be carried by AIS here & presumable O2 at the other end. My very old Nokia running the original pay-as-you-go number from a decade ago is on True-H- Tesco and DID allow keystrokes to the auto top up line. It was a very patchy connection and service, perhaps affected by the volume of traffic on the networks. After a dozen goes the credit DID also update from a new card after about an hour. The top up line wouldn't do a second top up for the SIM on the 5G phone. I presume there is a time restriction on using a new card until an initial transaction cleared.  Rome wasn't built in a day either : )

 

Thanks for the article Vinny41 on the impact of 3G phase out, Its probably showing age but I find it hard to figure out how significant the change will be and what the trouble free route ahead is.

 

KR

12 hours ago, CharlieH said:

Giffgaff. Worked for me me just fine for over a decade.

 

WHAT?????

 

I've given up trying to make it work......I just get not assigned to a (the?) network?

 

Any tricks/advice?

12 hours ago, CharlieH said:

Giffgaff. Worked for me me just fine for over a decade.

 

 

+1

12 hours ago, OJAS said:

Giffgaff works fine for me as well. You can port your Tesco Mobile number to their SIM. After activating it, you’ll be given a link to transfer your old number. You’ll just need your Porting Authorisation Code from Tesco Mobile.

 

You'll need to make a phone call or send an SMS with the SIM at least once every 6 months to keep it active.

 

https://www.giffgaff.com/

 

 

 

I have Giff-Gaff and TESCO mobile.

 

Don't ask me why  -  just instinct to have two numbers available. The numbers are linked to different institutions for OTP purposes and whilst I could change them to the same number it does seem a bit of a faff. Both sim cards are in a dual sim phone.

12 hours ago, CharlieH said:

Giffgaff. Worked for me me just fine for over a decade.

And me!

I,m on the same Sim Tesco Mobile PAYG ( 12 years ) ....if I need it topping up my son calls into the local Tesco outlet and buys a 10 pound top up slip and sends me the activation number....no problem 👍

1 minute ago, petermik said:

I,m on the same Sim Tesco Mobile PAYG ( 12 years ) ....if I need it topping up my son calls into the local Tesco outlet and buys a 10 pound top up slip and sends me the activation number....no problem 👍

 

 

Antiquated.....but it works.

 

I top up online.

1 minute ago, petermik said:

I,m on the same Sim Tesco Mobile PAYG ( 12 years ) ....if I need it topping up my son calls into the local Tesco outlet and buys a 10 pound top up slip and sends me the activation number....no problem 👍

 

Just now, hotandsticky said:

 

 

Antiquated.....but it works.

 

I top up online.

I used to do it this way also but hit a problem when my registered Bank Card expired and I had problems registering the new one with them....

Before I switched to Post-Paid, I used https://mobiletopup.com/?l=en to top up my PAYG AIS but you can use them for UK mobiles as well https://mobiletopup.com/topup/united-kingdom

 

Like others, I use GiffGaff for my UK Number. 

AI Overview

To check if you have an O2 3G SIM, look at the number printed on the SIM card; if it starts with 8930272040299 or lower, it is an older 3G SIM, but you may need to upgrade to a 4G/5G SIM by visiting an O2 store or contacting their customer service

O2 officially launched its 4G mobile network on August 29, 2013

For anyone that has an very old o2 3g sim these will stop working when o2 switched off their 3g network

 

1 hour ago, petermik said:

 

I used to do it this way also but hit a problem when my registered Bank Card expired and I had problems registering the new one with them....

 

That is what has happened to me at the same time as having the first ever problem keying numbers into the auto top-up service. Digits keyed from my 5G phone are not recognised by the top-up script at all but the key in did work on my old 3G Nokia intermittently. The connection was flakey and took upteem attempts but worked in the end. 

 

Check your phone keypad works, mine has always been reliable before. 

 

I think the intermittence is due to capacity issued arising in the phased switch off of 3G across the O2 carrier service mentioned in the article Vinny41 linked but whatever it is, I'll be stuffed when all 3G is switched off unless my 5G phone keys are recognised by the top-up auto service. Even the voucher route won't work without keypad recognition so I probably have to go for on-line top up & seeing if a friend in the UK can input a bank card from there while I send the OTP to my phone here for "Verified by Visa" process needs in the mytescomobile /Mi Pay.

 

 

Is setting a bank card up as fickle as tescosmobile's functionality on the Giff Gaff site? 

 

I presume tescomobile acceptance on a card fails because this laptop has a Thai IP address - does anyone know if that is it or use VPN to set cards up on UK sites like this from here?

 

I wonder whether tescomobile would accept a card from a thai bank - would that work?

16 hours ago, CharlieH said:

Giffgaff. Worked for me just fine for over a decade.

My Lidl sim works for since 20 years

Just logged in to My Tesco Mobile on my PC they sent a OTP and it was no problem regarding putting a voucher code top up for my number using my keyboard.......

15 hours ago, petermik said:

Just logged in to My Tesco Mobile on my PC they sent a OTP and it was no problem regarding putting a voucher code top up for my number using my keyboard.......

 Great, thanks. I hadn't thought of putting a voucher via a laptop. It'd avoid the handset keying trouble that has befallen me. 

 

This morning I've had a few more goes. Even the hearing the script instructions phases in and out of audibility and it seems there might be intermittence at their end in receiving key strokes - only a guess. It like a bad telephone connection used to be, the line phasing in & out. I get a flash back to being in phone box on a dodgy connection when that beep, beep, beep for more coins cuts it off : )) !

 

I'm trying different times of day & different handsets in case the old nokia is finally conking out too. 

 

KR

It looks like you can order a free SIM with UK number to be sent to Thailand from Giff Gaff or port an existing Tescomobile number to it if the payment process with Tesco gets too troublesome. 

Another happy GiffGaff user. Sim sent direct to Thailand (a few years back, so not sure if still the case) and topups via credit card.

On 9/18/2025 at 8:59 AM, Will B Good said:

 

WHAT?????

 

I've given up trying to make it work......I just get not assigned to a (the?) network?

 

Any tricks/advice?

Used for more than a decade... maybe order a new sim and try again?

1 hour ago, falangUK said:

Used for more than a decade... maybe order a new sim and try again?

 

Been driving me mad......will do......tried everything else.

On 9/23/2025 at 2:15 PM, PPGuy said:

Another happy GiffGaff user. Sim sent direct to Thailand (a few years back, so not sure if still the case) and topups via credit card.

 

Giff Gaff sent me a SIM here. I have just set it up without any problems. It accepted  payment by bank card up without any of the problems I had in using a new card on tescomobile. 

 

If anyone followed this thread, at one point the tescomobile Auto Top Up service ceased to recognise digits keyed in unsing the phone keypad. That problem had disappeared when I tried again in the new month of October, I suspect the system must have deactivated that functionality on my account for some reason in Sept. Who can tell? Life is too short not to switch to GG imo. 

 

KR

Does anyone know whether there is any drawback in transferring an old number (on a 3G or 2G) sim to a new 5G sim? Phone numbers are entirely independent of the grade of data mode in use in a SIM 2G/3G/5G, aren't they?

4 hours ago, 503726 said:

Does anyone know whether there is any drawback in transferring an old number (on a 3G or 2G) sim to a new 5G sim? Phone numbers are entirely independent of the grade of data mode in use in a SIM 2G/3G/5G, aren't they?

When transferring an old phone number from a 2G or 3G SIM to a new 5G SIM, the most significant risk is a temporary loss of service during the transfer process

Most UK network service providers do offer a 4G/5G conversion service to esim if your mobile phone has esim support which means if you convert your 4G/5G eim to an esim then you can use your phone without any physical sim being present in the phone

For some reason they don't offer a sim to esim conversion service for anyone using a 2G/3G sim

 

 

vinny you're the man on phones! Thanks once again, a temporary loss of service wouldn't be an issue for me on this, it just might be nice to keep my decades old number from my faithful Nokia!  🙂  KR

15 minutes ago, 503726 said:

vinny you're the man on phones! Thanks once again, a temporary loss of service wouldn't be an issue for me on this, it just might be nice to keep my decades old number from my faithful Nokia!  🙂  KR

Most network service providers allow you to keep same number when upgrading from 2g/3g sim to 4g/5g sim

if your changing phones at the same time just remember to order the correct size sim for your new phone

https://en.wikipedia.org/wiki/SIM_card

And remember some phone numbers are stored on the sim card and some phone numbers are stored on the phone