I ordered the new iPhone 11 Pro Max last week on ATT installment using my upgrade with them. I upgraded from the iPhone 10s Max which had approximately $645 remaining balance. My intent was to pay the remaining balance so that I could have the 10s Max unlocked to give to brother on Verizon. However, the second I pre-ordered the new phone the installment agreement immediately switched to the iPhone 11 Pro Max agreement. How can I now pay off old phone agreement and get it unlocked?