Wanting to upgrade to I-phone 13

Went into xfinity store and wanted to trade in a Galaxy A15 I had just bought 2 months ago after my iPhone SE was broken beyond repair, and I got two shocks. One you can only return a phone within 14 days of purchase (silly me didn't read the fine print and wasn't informed of that rule) ATT at least gives 30 days. Thus you own it, or have to pay it off to purchase a new Iphone if you don't own it and are making payments, and unless you add an additional line ( I have two no need of a third ) Xfinity won't take it in on trade for a new I-Phone. Upset me to no end spoke with Manager and he said that is the industry standard, odd that would do so if moving to another Galaxy but not an I-Phone, I said seems you are pushing Samsung to buyers and dissing us iPhone lovers. He stated that is a Apple thing they do the promotional setups and there isn't one on returning a Samsung for and Iphone. Man so, I pay $200 outright for a Samsung phone, use it two months don't like how it works and in returning it can't even get something off the purchase of a new Iphone? Please don't make me ditch Xfinity for ATT.