try to remove your sim card and put it back.

Tap on 'My Number' and key in your phone number?

hmm.have you try restore ur phone?

Hey I had the same problem and there is such a simple fix to it.

1. Turn on Airplane Mode - You will notice that you can not access your phone settings while airplane mode is on.

2. Turn off Airplane Mode and Immediately go to your phone settings and click on the unknown number tab and you will be able to manually enter your number. After this you should also get a message from imessage saying that you might be charged some amount or something like that. Say okay and you are all set to go. Hopefully this helps for regular messaging also, my regular messaging was already working only imessage was going through my email and not as my no. Enjoy!!!

are u sure? your phone sets is local set? or not?
i read in some forum they said this also can fix it.

1. Create a contact with your name, phone number, mail, etc. (I used the format "+ Country_Code + Area_Code + phone_number").  Really the format doesn't matter (I guess).

2. Go to:

     - "Settings"

          - "mail, contacts calendar..."

3. Search for the group "Contacts"

     -Select "my data"

          -Select the contact you have created in step 1.



That's all !!!!

please do more research on google there is many solution there.

Are you using a cut sim from umobile?

your phone is local set?

yes.

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Added on June 4, 2012, 2:17 pm

yes, local set.

That number is stored in the sim card. There is a way to put your number directly to the sim card but I already forgot how. Did it last time during iPhone 2G days. Maybe you can google it.

SOLVED! if there are any admins reading this fix should be made accessable as there will be others who eventually have the same issue regardless of the iPhone version… It happens to all of them! After getting zero help from Vodafone or Apple I took someones advice on a forum from overseas, put my MicroSIM into a phone that allows you to enter your own number (this will not work in another iPhone) fortunately for me I got a MicroSIM to normal SIM adaptor with my XT SIM pack I got free with the phone – thanks Telecom! I used a Blackberry Bold 9700, but heaps of other phones allow you to do it. Now my iPhone and iTunes displays my number rather than "Unknown" I can also change it (which I could never do before). The reason it annoyed me is because when your phone doesnt know its own number iMessage will only allow you to send and recieve messages via your email address and wont convert an iMessage to SMS… If the phone you message has no 3G data or isnt on WiFi they will not recieve the message! My apologies for the long story, but I felt it necessary to post the fix as it took me hours and hours to sort it out. Cheers .

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Added on June 5, 2012, 4:46 pmFrom what I can remember (vaguely), you need to put the sim card in another phone (not iPhone) and input the My Number there. Something that got to do with iPhone can't write to Sim or something.



Hope this help