iPhone 11 traded-in in August 2025, still waiting for monthly credits to be applied to my bill - please help!

I purchased a new iPhone 16 in July 2025 and opted to trade-in my iPhone 11 for monthly credits. The whole process has been a fiasco with me never receiving any email communication whatsoever from Xfinity about the process. I never received a shipping label to send in the old phone. I had to contact Xfinity and have a special label emailed to me. Once the old phone had been shipped out and received, I was told by agents that I would receive a confirmation email that it had been received and another email once Assurant reviews the phone and accepts it as a viable trade-in. The only email I have received from Xfinity was for my order confirmation for the new phone in July. I have reached out via chat and on the phone to speak with an agent on August 7th, August 18th, August 31st, September 30th, and October 24th. Transcripts of these conversations can be provided. During my August 31st chat the agent told me that the phone had been received, reviewed by Assurant and the trade-in approved and that I would see the credits applied to my next bill. They assured me that I would not have to contact Xfinity again about this issue. Yet, the credits still have not been applied. I chatted with an agent on September 30th who told me that I needed to call Assurant. When I called Assurant and put in my phone number, they said there was no record of a device associated with that number. I never got to speak to a person! I called Xfinity on October 24th after another bill posted without the credits being applied and spoke with an agent who once again told me that the trade-in had been approved and that I would see the credits on my November bill. Well, my December bill just posted and there are still no trade-in credits being applied!  I am so frustrated and just don't know how to get in contact with someone who can actually solve this problem for me. I just keep getting the run around from every agent I speak with. I hope someone on this forum can help me resolve this problem once and for all.