Returning iPhone 17 pro max

A few days ago, I ordered an iPhone 17 Pro Max over the phone through Xfinity. During the order process, I specifically requested to trade in my current iPhone as part of the purchase.

After receiving the new phone, I contacted customer support and was informed that no trade-in was initiated on my order. I then attempted to resolve the issue, but my request was declined.

At this point, I am trying to return the new iPhone 17 Pro Max, but my return request has also been declined. I would not have purchased the phone through Xfinity without the trade-in offer, as that was the main reason I chose Xfinity instead of another provider. What should I do in this case?