Calls End Up In Voice Mailbox - Phone Doesn't Ring

[welo]

I have a 12call prepaid SIM, several years old. During the past weeks I noticed that sometimes people call me but my phone doesn't ring. A couple of seconds later I get the 'this number tried to call you' SMS. I am 100% sure the phone didn't ring and it had perfect signal at that moment.

Actually I found out about this when subscribing to a VOIP provider that provides a callback service (you dial their Thai dialin number and the system hangs up on you, then calls you back and you can dial your international number - this saves on local phone costs). I was expecting their callback but no ring, no incoming call. Just the SMS ('this number tried to call you') after a few seconds.

This is after I had my voice Mailbox disabled. Before people would get routed to my mailbox even though my phone was on with perfect signal, but no incoming call.

This happened with (at least) 3 different international phone call providers, no matter whether calls originated in Thailand or from Europe.

AIS customer service is of no real help - they call me back on my number/phone to show that it works (well, yes, it happens OFTEN, but not ALWAYS), but don't give any information what might be going on.

Does anybody know if this is likely a network problem or if it can be due to a phone or SIM card bug/problem.

It seems the problem occurs only with international calls, but I might as well just pay more attention to those and might not notice problems with domestic calls.

welo

[kurnell]

I have noticed this happening a lot lately on my AIS connection

[welo]

In your case, is it related to international phone calls?

[BWPattaya]

Have you inadvertently set up a call divert to your mailbox?

[Pakaty]

You have voice mail? I'm jealous!

I have had the same AIS SIM card for 6 years and although I can set up my voice mail it will only work for a month or two or three. Then I have to set it up again. It just stops working as if I never had voice mail at all. I have given up and not bothered with it for about two years now. I guess I should give it another shot.

As far as the cause of your problem, I would start with the AIS network. If you suspect the SIM, AIS can provide you with a new one with the same number. They did it for me when my phone was stolen. They did it for free on the same day.

[welo]

You have voice mail? I'm jealous!

As far as the cause of your problem, I would start with the AIS network. If you suspect the SIM, AIS can provide you with a new one with the same number. They did it for me when my phone was stolen. They did it for free on the same day.

Well, my first guess would be the AIS network, but there is hardly anything I can do about it other than call the customer service. And for sure they blame anything else first rather than admitting a problem on their side.

That's why I consider troubleshooting SIM and phone.

Requesting a new SIM is a good idea. Maybe I will borrow a friend's phone to rule out issues with mine.

I still hope somebody knowledgeable will provide me with more information on why exactly this happens and where to start troubleshooting.

Thanks for all your input so far!

welo

[mrclough]

This is going to be a very hard problem for any party to diagnose. I would suggest firstly getting the SIM replaced. Technology has moved so much in the time since you purchased this SIM that it may no longer correctly support all the functions on the network you use.

secondly, as far as the handset goes I would try the new SIM in the existing hanset. That way it is easier to see if the problem lies with the new SIM or old handset. If the problem persists you would then obviously try a different handset to see if this eliminates the issue.

If it doesn't you are going to have to get your network to investigate the problem, this will be where your trouble really begins!

I used to work in the mobile communication industry in the UK and we used to request call examples with number calling you, time, date and location. We would also request to try and re-create the fault in other locations to see if the issue is localised on the network are not.

Your network should be able to investigate this problem and see what is happening via the routing of the calls being made to you accross their network, but they only would have the ability to investigate within their own network.

When you describe their customer service as being unhelpful, are you really considering how hard it is to describe this sort of problem and taking into account their understanding of the difference in language? In other words, have you a Thai person who can understand this and translate it for you? Maybe you speak fluent Thai for all I know but just a thought.

Last possible solution is to see if you could maybe port your number to another service provider? Not sure if they do this here though.

Anyways, Good luck with it all !

[welo]

Thanks for your reply!!

Your comment actually encourages me to request a new SIM card - seems to be worth a try! Then check the phone just to make sure.

I am aware of the complexity of troubleshooting phone network issues and I am not overly confident that AIS will be willing to put much effort into my case.

I suspect that the routing problem might relate to the gateways/end points (not sure about terminology here) used by international VOIP phone call providers in Thailand.

When you describe their customer service as being unhelpful, are you really considering how hard it is to describe this sort of problem and taking into account their understanding of the difference in language? In other words, have you a Thai person who can understand this and translate it for you? Maybe you speak fluent Thai for all I know but just a thought.

AIS has English speaking staff on the support hotline, and I was actually positively surprised about their very good English skills. The problem description is not that complicated either and I'm very much aware of the complexity of troubleshooting a technical problem like this - and very eager to answer questions or provide assistance in troubleshooting.

I had written a longer statement but decided to not post it - I has not been my intention to rant on the customer service here. If I am able to rule out SIM card and phone problems I will call them again for sure and be more persistent. Never give up hope

Thanks again for your input!!

welo

[gregb]

It is very hard to imagine a scenario where this is related the VoIP provider. The fact that it reached your voicemail means the interconnect between the Thai terminator and AIS is working fine. The call is now inside of AIS network. So, at this point, there should be no difference really between a call from one AIS subscriber to another and a call from the AIS tandem to your mobile phone.

I would check certain things.

1) Does this happen predominantly at certain times of the day? If so, it strongly indicates a capacity issue during peak hours.

2) Does it still happen if you test in a different part of the city? It is possible the cell towers in your area are full. Your phone is still registered on the network and can communicate via the SACCH channel, but when a call comes in and an attempt is made to get a B channel, they are all in use and the system gives up. This is a very common problem.

Capacity in the AIS network at a specific cell tower would be my first guess as to your problem. Only a trained AIS engineer with access to the entire network could tell for sure. They should be able to look at the C7 signalling between each point and see exactly who diverted the call to voicemail. Good luck convincing AIS that your small problem is worth a day or two of senior engineering time.

You simply aren't that important.

Try making your calls from a different place in the city or between 3 and 4 am when the network load is the lightest. I bet all your problems go away.

[welo]

It is very hard to imagine a scenario where this is related the VoIP provider. The fact that it reached your voicemail means the interconnect between the Thai terminator and AIS is working fine. The call is now inside of AIS network. So, at this point, there should be no difference really between a call from one AIS subscriber to another and a call from the AIS tandem to your mobile phone.

My guess was that something might go wrong at the interconnect, but what you write makes sense - in such a case it would not end up at my voicemail but not reach the AIS network at all.

It might be paranoid to think that maybe AIS has an interest in not always routing these calls correctly - I mean deliberately

(Did I mention that the twin towers were never hit by any airplane but...)

I would check certain things.

1) Does this happen predominantly at certain times of the day? If so, it strongly indicates a capacity issue during peak hours.

2) Does it still happen if you test in a different part of the city? It is possible the cell towers in your area are full. Your phone is still registered on the network and can communicate via the SACCH channel, but when a call comes in and an attempt is made to get a B channel, they are all in use and the system gives up. This is a very common problem.

I definitely have to run my own tests on this problem. Get my friends phone and call my cellphone several times during the day and see if I can provoke the erroneous behavior.

The problem doesn't happen that often so I could answer your questions about peak hours.

I live in a village in the countryside. I guess there is more than one sender around since I remember reading on the phone a sender named [village name 4].

Again, unfortunately (or fortunately) the problem doesnt' happen on a very regular basis, so hard to test the sender theory.

Thanks for your explanation on the different channels. I didn't know that and this could easily explain the problem.

You simply aren't that important.

I am VERY important

..to my wife

..to my parents

...

Thanks for your feedback!

welo

[welo]

Just want to give an update. Tracked the problem down to the SIM card (90% sure). It was difficult to troubleshoot since I could NEVER recreate the error when calling from a second (local) phone. However, using a callback service from a thai VOIP provider gave me a high chance of error.

This is still kind of weird to me - why this high error rate with international call providers? Other friends abroad said they have to try 5 times and more to reach me (while others gave up before). Calls within Thailand don't seem to have this high failure rate...

I will have the SIM card replaced - I'm curious whether the problem is really solved then.

welo