How can I use my store credit towards my Apple Trade in value for my iPhone 14 Pro Max?

Hello,

i originally traded in my 11 pro for a 14 pro and financed the rest.

Now I exchanged my 14 pro for the max version. Apple in store and online made it seem like it was the easiest task.

Now I am stuck with apple credit and 7 plus hours spent at the store for them to tell me tough luck and that I don’t have trade in anymore and will have to use my credit card to pay for the trade in value because I was refunded my original trade in value. I’m just frustrated they couldn’t tell me this online and made me wait 7 plus hours in store for no resolution.

How can I use my store credit towards my apple trade in value for my 14 pro max.

Thank you.

[Re-Titled by Moderator]