Android - "My phone number" = Unknown or blank. How to fix

[Hands0n]

It is particularly odd how the little things in life can be majorly annoying. The "My phone number" field in Android being blank or "unknown" is one of them. It has been driving me nuts ever since I discovered it.

If you go to Settings, About phone, Status then you will see that the third field down from the top is "My phone number". Unless you are somewhat lucky it will say either "Unknown" or be blank. How annoying is that? Very!

So tonight I went on a quest to solve the annoyance for once and for all.

The solution, believe it or not, was my iPhone :D Although, to be fair, it doesn't have to be an iPhone specifically. Any handset that will allow you to set "My number" up on the SIM will do.

The specific instructions for an iPhone are as follows:-
Load Settings.app
Press Phone
Press My Number
Enter in whatever number you want, you can use the +44 notation
Press Save
Press Home
Job done!

Pop the SIM back into your Android and you will see the number that you programmed.

Simples :)

[Ben]

That's so bizarre, I didn't realise it was stored on the SIM. My O2 one always just worked, but I had to set it on my Vodafone one when I moved (escaped).

Nice :)

[Hands0n]

Yea, after a lot of research I came up with the information that the actual mobile phone number, in this case, is stored in the SIM's MSISDN (http://en.wikipedia.org/wiki/MSISDN) - that is its ""Mobile Subscriber Integrated Services Digital Network Number". Mobile telephony is loaded with acronyms. If you think you knew networking then you'd be sadly mistaken where it comes to mobile :)


the msisdn is not stored anywhere on the simcard, in fact the simcard does not know the msisdn. it is only used as an alias for us humans, so we don't need to remember the 15-digit IMSI. it is translated by the HLR or HSS, which is the central database of the network. the HLR knows the matching IMSI, which is basically the unique serial of the SIMCARD (masked by the TIMSI, temporary-IMSI, but that doesn't matter here) and thereby can identify and page the simcard/your mobile.

The MSISDN is not used by network operators to locate your true mobile number though - instead it is just a local and optional storage for your mobile number.

The mobile networks use your IMSI (http://en.wikipedia.org/wiki/International_Mobile_Subscriber_Identity) (International Mobile Subscriber Identity) is the unique SIM number that the mobile network operators use to identify your subscription and link it with your true mobile number. All that is done within the network itself. Think of the IMSI like a network card's MAC address and your mobile number like the IP number of the network card in your PC. It is a simple job for the mobile network operator to re-associate your mobile number with a new SIM by referencing the IMSI of the replacement SIM for example.

It is all quite layered and logical. If coming at this for the first time try and draw it out on a bit of paper while reading the Wikipedia articles or Googling. It is all quite fascinating in a very geeky way :D

[Ben]

We often refer to mobile numbers as MSISDNs in the industry, I suppose for added clarity. The operator HLR can be queried to obtain the IMSI just like we query DNS to obtain the IP for a domain name.