Trade in

My phone trade in was not processed as a trade in back in September. The promotion that was currently running was up to $1100 for a new device. I have been going back and forth between in store and Xfinity mobile support team for the last 4 months. The store was able to send my old phone (iPhone 14 pro max) in to assurant back in October but yet no resolution or credits. I think maybe around 6 or 7 tickets have been submitted up to this point and I get an email each time stating that the case has been resolved and an additional email will follow but never follows. The store and mobile support team keep pointing the finger back at each other. Why can’t the store make it right since they are the ones that messed up? I would like this escalated to the executive corporate team as this has been ongoing for so long and each time I deal with a rep, they state that the credits will soon be applied. Do I look into legal action at this point? File a complaint with BBB, FTC? Please help me resolve this.