I’m so disappointed

I’ve been a loyal client for almost 8 years I wanted to make an upgrade at mtn clear water fine I told the consultant I want a phone so I can give my daughter the old one then she showed me iPhone 15 I told her it’s small as she can see I’m using a pro max then ended up opting for iPhone seventeen I go to the store today she’s on leave fine they offer to assist great the open the phone it’s small like the 15 the consultant previously showed me I then told them this phone is small I need a big phone I was told it’s my responsibility to know the sizes and the phone I want that was the manager words I told them I don’t want it 3 years of paying for a phone you don’t like , overall they took the phone however didn’t want to give me the one I want so mtn please do something or cancel my contract ***