I want to upgrade from 12 to 15 with metro pcs. Also thinking of doing a trade in with my old iPhones as well.

Hi, I want to upgrade my iPhone 12 as it’s only 64gb and I’ve been running into storage problems for a while now. I asked my carrier (metropcs) how much would an iPhone 15 roughly would be to plan out money wise. The guy said $1,400 !?!!? I looked on Apple website and the one I want (iPhone 15 128gb-256gb) is between $800-$900. I also want to trade in my iPhone 12 and possibly my iPhone 8 as well. (To save some money and get rid of them).

I would like some advice on how to do so. I was thinking of just going to my nearest Apple Store and doing it all in person when I have to extra money. Do I have to notify my carrier before I buy my new phone? Or does Apple do all of that? I also heard that Apple has eSIMs now too for newer phones? So how would all that work out?

Any help would be great! Thank you!