Will Dual Sim Phones work after 2G is switched off?

[buckwhelk]

Hello,

I have a dual sim phone with 2 x 3G sims installed. As far as I am aware, most (if not all) phones can only have 1 x 3G sim connected and the second sim has a 2G connection, So if 2G is switched off, does my dual sim phone become a single sim phone?

[Lannig]

If only one SIM can do 3G, either statically (e.g. SIM #1 is 3G, SIM #2 is 2G per design) or depending on the phone configuration (you can switch one SIM as 3G and the other one as 2G) then yes, your dual-SIM phone will essentially become a single-SIM phone.

Some phones can do 3G on both SIMs, but that's not the most common case.

You probably need to refer to your phone's documentation.

[Aachen]

It works for me (Samsung Galaxy J7).

[Jdiddy]

I believe theres dual sim phones coming out that can do simultaneous 4g (data only) and 3g (voice, sms only)

The trouble lies where both sims try and access and transmit on the same radio channel, hence the need for seperation. When on 4g your phone still talks to the nearest 3g tower to standby for incoming calls, this can be switched off but no one can call you on that sim

[Gary A]

I can't really answer that question. What I can say is that I have an IQ X Slim 2 phone that is a couple years old. It was a cheap phone. I have a Dtac SIM in one slot and an AIS in the other slot. I can call and receive calls with either card. Swapping the cards from slot to slot does not seem to make any difference.

[Srikcir]

Have a Samsung GT-E1200Y phone with 2g SIM by DCAT.

Went to DCAT center and they transferred 2g SIM stored phone numbers to a new 3g SIM - free

[silverhawk_usa]

As usual, Google has some good answers and explanations. https://www.quora.com/Why-cant-we-use-3G-4G-on-two-Sim-cards-together-in-the-same-mobile

My Samsung J5 is a Dual Standby as explained in the link.

[mtls2005]

What is the make and model?

Do you use two SIMs now?

Which service providers?

You say your phone supports two 3-G SIMs, so I'm not seeing the relevance to 2G?

DTAC's GSM1800 franchise runs until 2018 (maybe September?). I think they are still using some of that spectrum for 2G, but much of it is transitioning to 4G. Last I saw they had 2.4 million 2G customers.

AIS still has some 2G customer on GSM900, maybe until they end of June. They did "win" the JAS 900 MHz default auction, but not sure they'll use any of that to continue to offer 2G? They may have a roaming agreement for their 2G customers to roam onto DTAC?

Any 2-SIM phone with a 2G-only slot should work on DTAC until 2018, assuming coverage. I'm not 100% sure on the AIS roaming deal with DTAC so cannot say for sure how one will fare on AIS with 2G?

On the 4G front, LTE service has to fall back to 3G for voice calls - this is why it can sometimes take a while for a call to go through - especially between providers. VoLTE will resolve this challenge, but (AFAIK) only DTAC has implemented VoLTE, and the phone needs to support VoLTE (higher end models only), and you need to register for the service with DTAC.

[TallGuyJohninBKK]

I have an ASUS Zenfone 2 Laser dual SIM phone. According to its manual, the SIM 1 supports LTE, 3G and GSM.

But SIM 2 will only support a 2G SIM. So I'm assuming that means SIM 2 is becoming, as time passes, increasingly unusable.

[Issanman]

I also have the ASUS Zenfone 2 Laser and it will do 4G from either SIM slot, but only one at a time. Here is a quote from the SPECS.

Both micro SIM card slots support 3G WCDMA/ 4G LTE network band. But only one micro SIM card can connect to 3G WCDMA/ 4G LTE service at a time.

[TallGuyJohninBKK]

There are quite a few different versions of the Zenfone 2 Laser.

You posted a link to specs for the ZE500KL.

I have the ZE550KL, a worldwide version sourced in Thailand.

Here's what its manual says on the subject:

I will admit, though, I haven't tested this myself as yet on my SIM2 on the phone.

And it appears the comparable ASUS website specs page for the 550 also says it should be compatible with 3G/LTE on both bands... So, I'm confused.

https://www.asus.com/Phone/ZenFone-2-Laser-ZE550KL/specifications/

PS - I went back and double-checked just now, and the Adobe PDF user manual document that I posted the clip from above has a title page saying it applies to the ZE550KL and the ZE551KL.

So either their specs page or their user manual is wrong. Guess I need to try a 3G SIM in my #2 slot to find out.

Edited June 17, 2016 by TallGuyJohninBKK

[Issanman]

^^I bet it will work on yours also.

[buckwhelk]

What is the make and model?

Do you use two SIMs now?

Which service providers?

You say your phone supports two 3-G SIMs, so I'm not seeing the relevance to 2G?

DTAC's GSM1800 franchise runs until 2018 (maybe September?). I think they are still using some of that spectrum for 2G, but much of it is transitioning to 4G. Last I saw they had 2.4 million 2G customers.

AIS still has some 2G customer on GSM900, maybe until they end of June. They did "win" the JAS 900 MHz default auction, but not sure they'll use any of that to continue to offer 2G? They may have a roaming agreement for their 2G customers to roam onto DTAC?

Any 2-SIM phone with a 2G-only slot should work on DTAC until 2018, assuming coverage. I'm not 100% sure on the AIS roaming deal with DTAC so cannot say for sure how one will fare on AIS with 2G?

On the 4G front, LTE service has to fall back to 3G for voice calls - this is why it can sometimes take a while for a call to go through - especially between providers. VoLTE will resolve this challenge, but (AFAIK) only DTAC has implemented VoLTE, and the phone needs to support VoLTE (higher end models only), and you need to register for the service with DTAC.

It's a Samsung Galaxy S Duos 2 GT-S7282L

I have an AIS 3G sim in slot 1 and a DTAC 3G sim in slot 2.

Only Slot 1 can connect to a 3G network, so I have the AIS sim in slot 1. Slot 2 can only connect to a 2G network. If I want to use DTAC 3G I have to put the sim in slot 1 and the AIS in slot 2. Hence my OP

[Lannig]

So this phone would be of the SIM #1 is 3G, SIM #2 is 2G static configuration? no way to switch 2G/3G from one SIM to another?

Can't find anything on this on the web.

Anyway, in either case, your DTAC SIM will continue working in slot #2 in 2G mode until some time in 2018 as mentioned above and you want to keep your AIS SIM in slot #1.

After 2018, your phone probably will be a single-SIM model as far as Thailand is concerned.

[buckwhelk]

So this phone would be of the SIM #1 is 3G, SIM #2 is 2G static configuration? no way to switch 2G/3G from one SIM to another?

Can't find anything on this on the web.

Anyway, in either case, your DTAC SIM will continue working in slot #2 in 2G mode until some time in 2018 as mentioned above and you want to keep your AIS SIM in slot #1.

After 2018, your phone probably will be a single-SIM model as far as Thailand is concerned.

After checking the user manual, I've discovered found that it is not a static config. If I set sim 2 as the data service network it connects in 3G mode. So as you say the phone should work OK in TH as a dual sim phone until DTAC 2G network is shut off. Thanks

[TallGuyJohninBKK]

^^I bet it will work on yours also.

I finally got around to trying a second SIM in my Asus Zenfone 2 Laser - ZE550KL - and it strikes me as still really only being able to use one 3G/4G SIM.

I had SIM 1 set to use 3G/4G, and when I put another SIM capable of 3G/4G in SIM slot 2, I got the following error message from the OS:

So AFAICT, on my model, either SIM can support a 3 or 4G connection, but in the device settings if you have 2 SIMs installed, it appears you have to restrict one of them to a 2G service only.

I'd be OK if the phone would only allow me to USE one 3/4G service at a time, if I could have both SIMs enabled for it as needed.

But the way it appears, you have to set one of the two SIMs as disabled for 3/4G, even if you're not actively using the other primary SIM for 3/4G.