My suggestion is to not trade-in a mobile phone, thru Xfinity. I suggest you sell the phone outright, instead, as phones shipped this way (with the Xfinity/Assurant return shipping label), tend to get lost for various reasons and you'll end up paying for the phone, in the end.
I had some difficulty shipping a trade-in iPhone back to Xfinity and also trouble returning a defective iPhone back to Xfinity. As far as the trade-in, the label wouldn't scan correctly at USPS (United States Postal Service). It kept coming up as "INVALID" when they scanned it. So, after making uneventful phone calls to Xfinity Mobile agents and their supervisor, I went to an Xfinity Store to see if they would take the trade-in, as I told them the shipping label to Xfinity Assurant was "Invalid". And the Xfinity store offered no help, either. So, I checked with Xfinity users, and they suggested to ship the iPhone back to Xfinity/Assurant using UPS, United Parcel Service, instead of USPS.
I took out $700.00 insurance and shipping thru UPS, and it ran me about $42.00. The reason I took the insurance out, was because of a prior (defective) iPhone, I had tried to return to Xfinity, in Coppel, Texas, which never reached the Xfinity store. The package, with the Xfinity return label, got all the way to Coppel, Texas, but only made it to the USPS Distribution Center. And from there it was lost, indefinitely. I tried going thru USPS's lost mail searches and tracking for over a year. In the end Xfinity charged me over $1400.00 for that phone, even though I showed them all the tracking information. So, this time I figured I'd put additional insurance on the shipment, whoever was responsible for the shipping service.
I'm just letting everyone know about this situation, in case they ever think of upgrading their equipment. I suggest you sell your equipment yourself, instead of trying this trade-in process, shipping thru and to Xfinity/Assurant. Don't believe what the salespeople tell you, when you call up asking for technical support or help upgrading, and they try to sell you a new phone or equipment and say shipping is full-proof for your trade-in/defective phone.