Sony Xperia Arc S, changing the "my number" in contact list? I've recently purchased a second-hand phone and my number is different than the one shown. How can I either remove it or change it? I've tried to add a field to it but that doesn't work either.
If you have not done a Factory Reset, the Android operating system is still in the same state as it was when whoever owned the phone installed it. Do the following to completely wipe the phone and thereby force the phone to recognize what phone# is relevant for the sim card inserted:


From the main home screen, tap menu
Tap Settings, then Privacy
Tap Factory data reset
Tap Reset phone
Enter your password if required, then tap Erase everything to confirm