How to return the free apple watch SE3 from promotion?

Hello, 

I got a call from Xfinity official phone number about a free apple watch promotion but with only $10/mo for 3 years. He said it has data and wifi so I was expecting it to have a new phone number but seems it needs to be connected to my phone. And looking at other support forum posts, seems many people are struggling on returning the apple watch as well. 

After being a xfinity customer for many years(mobiles, home internet, etc), I am not sure why they are doing this to me. 

On the phone call, the agent mentioned there is 7 day free cancellation. 

I would like to return it. How to proceed? Should I bring the apple watch to the Xfinity store?  

I am not sure where to request return label or anything like that. 

Thank you for your assistance.