Trade In Not Credited

I got an iPhone 16 Pro Max at the Xfinity store because they told me I’d get a trade in credit for $700. I sent the phone in and got it back in the mail 6 weeks later saying my find my iPhone needed to be disabled. I disabled it and called support and they told me I’d get a new box. I waited a month or two and called and they told me it’d be ready in a week or two. I was busy so another month or two go by and they tell me they have to make a new request. I wait another 2 months or so and finally they tell me to go to the store and ask for a label which is what I had asked the previous reps if I could do and was told no. Now I finally get the label a month or so ago and I send it in and I’m being told the trade in is not eligible. Every person I talked to I asked them specifically whether or not I’d still get the credit and I was reassured that I would. I called and spoke to several customer service reps who made tier 2 tickets which were closed with absolutely no other information attached. What am I supposed to do now? Why did they even have me send it in if it wasn’t eligible? I’d much rather have just kept it.