Here is my situation. I am an international student, I happened to lost my phone during my trip in summer 2014. So I brought an iPhone as a replacement. I thought I bought the unlocked one since I knew I would left the United States after I finished my study.
As I went back to Indonesia around a month ago, I brought my phone to like local stands that sell local number and to my horror they said my phone was locked therefore I couldn’t use it at all in Indonesia.
Like hell, so I contacted my carrier, T-mobile, and chatted with them. I asked if I could unlock my phone since I left U.S. and I need to use simcard other than US simcard. I used livechat, and the agents were really friendly and swiftly tell me what to do.
To Unlock iPhone bought in the US, I need:
1. PIN number (the one that I made when I first activate/bought the phone. I almost forgot it but lucky enough I can guessed my PIN number correctly lol. note: write down your PIN for phone).
2. IMEI code (available from phone by dialing *#60#
voila~ you will have an email that said your unlock request had been granted and procedure to unlock/erase your phone content. Below is the content of the email:
Thank you for taking the time to contact T-Mobile. 24 hours after receiving this email follow the below instructions for unlocking your T-Mobile iPhone which said:
If a non-T-Mobile SIM card is available:
1. Insert the SIM into the iPhone.
2. Complete the setup process.
If a non-T-Mobile SIM card is not available:
1. Connect your device to a computer running iTunes.
2. Complete a backup of the device information using iTunes.
3. Disconnect the iPhone from the computer.
4. Complete a master reset using the Erase All Content and Settings option.
5. Once the master reset has completed, reconnect the iPhone to the computer.
Note: Do NOT complete the initial setup process prior to plugging the device in.
6. When successfully unlocked, the message Congratulations, your iPhone has been unlocked will appear.
Note: It may take a few minutes for this message to appear.
7. Complete a restore of the device information.
If your iPhone doesn’t unlock, complete a backup through iTunes or iCloud again and follow previous steps.
Then your phone is unlocked.
The minus is maybe you will also lost your Find my Phone service that allows you to locate your phone.
Hope that helps.