IMEI carrier check allows you to find out to which carrier your iPhone is currently locked, At&t contract status, etc. You can also check Sprint IMEI status for free.
Please, note this is NOT an unlock.
? You can find out your IMEI number by dialing *#06# on your iPhone. It's important that you do NOT use the IMEI printed on your box from iPhone, as these boxes changed often at the stores.