Phone trade in/Assurant offer Number

I have spoken to Xfinity Mobile customer service twice now regarding my trade in offer. I received the Iphone 17, and as part of it I had sent in my Iphone 12 as a trade-in for a credit towards the phone. I was told by an Xfinity customer service agent I had to call Assurant and give them an offer #. He told me the offer I received in my email from the Iphone 12 would be honored. I have called Assurant multiple times and there is no one to speak to in order to provide this offer number. I also tried the live chat agent from Assurant who told me that Assurant does not deal with this and to call Xfinity. How can I provide this offer number to a company that does not provide someone to speak to? All I want to make sure is that the offer sent to me in my email for the credit towards the new phone balance is applied to my account. It does not even let me accept or reject the offer but tells me I have until the 13th to do so.