Before you can use another SIM card in your existing phone you may need to get your previous network or service provider to unlock the handset. You will need to wait until the expiry of any existing minimum term you have agreed and a charge may be payable.
If your iPhone is a Pay as You Go, then you can request to your network provider to unlock your iPhone. They might ask where and when did you purchase, and the IMEI on your handset. After requesting, there is a charge fee of 15 pounds (depends which network) and I wait for 48 hours for the confirmation text to come that my iPhone has been unlock. Then connect to the iTunes and Restore your handset, don't forget to backup as your files will lost like contacts, messages, photos, etc.
And the result:
Do not attempt to unlock your iPhone in some shops to avoid damage and it will lost your warranty.
Warning when you will NOT properly unlock your iPhone:
- It requires that you have a bit more technical expertise than some of the other solutions that have been used.
- One thing to note as well about this solution is that it will not work for firmware versions: 5.15.04, 5.14.02, 3.10.01, 2.10.04 or 4.10.01.
- Also this cannot be the first time you have jailbroken your device, it must already be jailbroken.
- If you are running baseband 6.15 you may end up losing GPS capabilities.