Here are some of iPhone Keypad codes.
*#06# – Displays your iPhone’s International Mobile Equipment Identity (IMEI) number
*#21# – Displays any call forwarding settings enabled on your iPhone
*#30# – Shows you if you have the call presentation (to see who is calling you) setting
*#33# – Displays call barring settings for your iPhone
*646# – View available minutes on your AT&T plan (also *min#)
*3282# – View wireless data usage statistics (also *data#)
*225# – Check the bill balance on your AT&T account (also *bll#)
*729 – Makes a call to AT&T to pay your wireless bill
*639# or *new# will show upgrade eligibility
[Via makeuseof]