Fraud and theft

Xfinity illicitly continued to charge us for the past 5 years for 2 cable boxes that we returned January 2020. They finally actually removed them from our bill in December 2024. I did the math, it adds up to over $1000. We are trying to get a refund. Customer service and escalation dept claim it was negligence on our part for not reviewing our bill and reporting sooner, but we did in fact report the issue over and over these past 5 years, and each time we were told that the boxes were taken off our bill, and we wrongfully trusted Xfinity to be truthful. We have ended our service with Xfinity (with difficulty, and drawn out over the course of 2 months), and we paid our balance. Now we just want the money back that they stole from us and lied about. Customer service refunded a small fraction of what is owed. They were extremely rude and even told us to stop calling, but we want this issue resolved. Who exactly do we need to contact to get our $1000 back?