Return Phone after 14 days

I got a phone from Xfinity on 10/4 and couldn't pay much attention to it due to family concerns. The device was self-activated on the 18th. While looking at the bill I found that the bill was much higher than what I was told it would be originally. I cancelled the account on 10/24; I have the proof of cancellation if needed. I was told that I would get a return shipping label and will be charged $35 for restocking fees. I waited but never received any shipping label. I went to a Xfinity store they told me to talk to a support number. After a week I again called Xfinity and requested for the shipping label they again assured that I will get the shipping label. Nothing happened at all. Today, 11/17, I again called Xfinity and requested to get the return shipping label, but they said I cannot return the device since 14 days have passed. They even confirmed that I was told multiple times that I will get the return label, but the request was denied. I am stuck with the device and don't know what to do. I am being unnecessarily charged 35 dollars per month and after being a Comcast customer for the past 14 years, I am extremely disappointed. I am stuck with $750 device which I do not need I want to return the device and would like to do so as soon as possible.