Hello Jennnnnnay,
Thanks for using Apple Support Communities.
I understand you're getting a message that your iPhone is giving you a message the the SIM isn't supported. For assistance with this issue please follow the steps outlined below.
Follow these steps if you have any issues or if you see this message in iTunes or on your device:
"The SIM card inserted in this iPhone does not appear to be supported. Only compatible SIM cards from a supported carrier may be used to activate iPhone. Please insert the SIM card that came with your iPhone or visit a supported carrier store."
- Restore your iPhone to factory settings.
- Contact your carrier to make sure that the unlock was applied in your carrier's system.
- Restore your iPhone from a backup.
How to unlock your iPhone for use with another carrier
Take care.