I bought "factory unlocked" iphone 5 from guy on kijij. Tested it with fido sim and worked. Then with another sim from another carrier and it's not working with other sim. A company who unlocks iphones said it's locked and I will have to pay to have it unlocked. Can testing it with fido sim have caused it to be locked? Please help me understand what could be wrong. It was still sealed when he gave it to me, and came with a receipt from some small computer store where he bought it ( not apple ).