I have iPhone 6 which is out of contract and I do not owe any money to Sprint. I am trying to unlock it so that I can use on another US carrier and spent several hours on the phone for this. I filed 2 tickets for unlocking the phone (the last one specifically for domestic unlocking) and received 2 emails confirmations that my phone is unlocked. When I put in the SIM card from the new carrier, the I still get the error message that the SIM card is not supported. Can someone look into this and resolve it?