On the wiki I have found This Info to set the Mailbox Number on the Iphone:
For those who've unlocked and have a non-functioning Voicemail button, here's how to fix it:
1. First, take note of what your voicemail number is with your current provider (for example, in Spain the Vodafone voicemail number is 177).
2. Click the phone button in your iPhone.
3. Click the keypad tab.
4. Type the following code: *5005*86*xxx#
Where xxx is your voicemail number, using the Spain Vodafone example, you would be typing *5005*86*177#
5. Hit call.
6. Give it a bit, and the code will be set.
7. Hit the voicemail button, and it will now call your voicemail.
The problem is That My Orange Mailbox Is called Using *777. How the Heck I can Do that on The iphone??? If I hit *5005*86**777 it seems that the iphone Dials 777 and I get an error from orange saying the number is incorrect.
Can Anyone Help????