Is switching to Verizon my best option

I have been a customer since 2009 and currently have 7 Lines with Att. In September I upgraded 3 lines to the new Iphone 14 Pro. One of the lines I upgraded was the wrong line and after receiving the phone and realizing my mistake I went to the local Att store and told them I wanted to cancel the order. They told me I didn't have to do that  since I already received the phone they would just transfer the phone to the correct number. They then activated the number on the new phone which now had 2 numbers assigned to it. After a number of customer support calls they finally got the correct numbers assigned to the correct phones, and all was good, I thought. My Father passed away and I need to cancel his line, when I go onto my account it appears his line is the one that the installment plan got put on while he didnt have a new phone, the number with the new phone is showing eligible for an upgrade now. I called Att and they said that I would have to pay the full price of the phone, losing my $350 credit for the trade in, in order to cancel that line. I explained to them that I would have canceled the order and changed it to the correct phone if their store employee hadn't told me otherwise. After 13 years of loyalty I would have hoped for a better resolution than, "I am sorry there is nothing we can do".