next up

I (unknowingly)had next up and paid for 22 months out of 36. I went to trade in and upgrade to iPhone 15 pro-max. I had to pay off my iPhone 13 Pro first ($566). I got $1000 off for my trade in. When I noticed their mistake, I went back to tell them I had paid for the next up all those months, so should not have had to pay off my balance.They said, Had they waived my balance through "next Up", I would only have gotten $500 off towards my new phone with trade in instead of $1000. So, what was the point of the next up? Only AT&T wins with this. Wish I would have went with buying phone with manufacturer instead. I am tempted to pay off and go with Xfinity or Mint mobile. I hate this "in your face" rip off. But, I pay for two family members phones and lines AND I'm a nurse, so have FirstNet with AT&T. I do like FirstNet service. But, feeling they owe me that $6/month I paid for 22 months. I want to be refunded that $6/month. It did nothing for me. I had to pay off my old phone balance after 22 months of paying with next up.