iPhone Carrier Locked Trade-In

I have a dilemma with Mint mobile where they charged me twice because I had to resubmit an order with the correct email address because I don’t have access to the email that autofilled by accident anymore. They said they’d refund the first charge, and they didn’t and now they say there is no record of it. I disputed one of the charges and after the bank heard little to no response from Mint, the credit was made permanent to my account. Now that the dispute has been completed, Mint has cancelled my mobile plan that I paid for upfront, leaving me without a mobile service and now saying I owe the balance of the phone and plan even though I have proof of the charges on my bank statement.

So to my point, my phone being carrier locked and Mint with no record of a second transaction and being particularly unwilling to work with me, if they absolutely won’t do anything about it and this being the worst case scenario, can I trade in a the the new and carrier locked iPhone 14 I purchased from Mint for a phone that’s unlocked so I can just go back to my old carrier and be done with this? My phone is still under limited warranty so I don’t know if that helps. Any responses or helpful information is appreciated.