1. *3001#12345#* and tap Call. Enter Field Mode. Field mode contains lots of iPhone inner settings, especially newest network and cell information. 2. *#06# Shows your IMEI. No need to tap Call. IMEI is the unique identifier for your mobile phone hardware. 3. *777# and tap Call. Account balance for prepaid iPhone only. 4. *225# and tap Call. Bill Balance. ( Postpaid only ) 5. *646# and tap Call. Check minutes ( Postpaid only ). 6. *#21# and tap Call. Set interrogation for call forwards. Discover the settings for your call forwarding. You’ll see whether you have voice, data, fax, SMS, sync, async, packet access, and pad access call forwarding enabled or disabled. 7. *#30# + tap Call. Check the calling line presentation. This shows whether you have enabled or disabled the presentation of the calling line, presumably the number of the party placing the call. 8. *#76# and tap Call. Check whether the connected line presentation is enabled or not. State whether the connected line presentation is enabled or disabled. Similar to the calling line presentation. 9. *#43# and tap Call. Determine if call waiting is enabled. Shows call waiting status for voice, data, fax, SMS, sync data, async data, packet access and pad access. Each item is either enabled or disabled. 10. *#61# and tap Call. Check the number for unanswered calls. Show the number for voice call forwarding when a call is unanswered. Also show the options for data, fax, SMS, sync, async, packet access and pad access. 11. *#62# and tap Call. Check the number for call forwarding if no service is available. Just like the previous, except for no-service rather than no-answer situations. 12. *#67# and tap Call. Check the number for call forwarding when the iPhone is busy. And again, but for when the iPhone is busy. 13. *#33# and tap Call. Check for call control bars. Check all the usual suspects ( voice, data, fax,SMS, etc ) to see whether barring is enabled or disabled for outgoing. THIS CODES ARE JUST MEANT FOR USEFUL PURPOSE AND TRY AT YOUR OWN RISK. THIS CODES MAY WORK OR NOT ACCORDING TO THE PHONE MODEL.