iPhone 3G Number change

the number shown is the number of your contract with your mobile operator !
if you have another phone number thus another sim card it will show the other number !!
the number does not come from the phone but from the sim card that's inside !

I have the same issue.

My iPhone displayed the number that it came with, but when I transferred the number from my previous phone both iTunes and the iPhone itself still display the original number - which is now wrong. I need to be able to edit this. The SIM card is now the new number, but there does not seem to be any way to get this to update the displayed number in Itunes and on the phone 😟

Perform a Restore in iTunes and set up as a new phone (not from backup).