Urgent: Mobile trade-in promotion changed without consent, need corporate assistance

I'm looking for help from someone with corporate-level authority.

I upgraded a device on December 1 under a specific Xfinity Mobile trade-in promotion. I was explicitly informed by a phone customer service rep that this original trade-in promotion would be honored with an exchange for a different device. Instead, the new device is attached to the newer promotion which started on December 3. This account change was made without my consent.

I have spent hours on the phone with customer service attempting to resolve the issue, only to be rerouted to irrelevant departments and hung up on without follow-up (while on hold for 20+ minutes) several times. I have been to two stores in the past week. Nobody seems to have the authority or desire to exercise the authority to honor the original promotion.

If this isn't resolved promptly, I will file a complaint with the FCC and transfer my service.