Xfinity [Edited] and doesn't care when they get caught

We went into the local xfinity store to suspend our sons phone line. While we were there they talked us into an additional line for "free" that we named "extra". [Edited: Inflammatory]! Well the next month came around and they didn't suspend the line so we went back in to find out what was going on. They said unless he was in the military there was nothing they could do for us. So we canceled the line and tried to return the phone they gave us "still in the box, never used.". And they say "oh sorry, it has been more than 14 days we can't take it back." We immediately canceled all 6 lines and ported our numbers out to another carrier. Well this turned into fighting with the store and then Xfinity corporate for a few weeks finally ended up with a supervisor on the phone that agreed with our point of view. He waived any remaining charges and told us he deleted our card on file to make sure we didn't get charged for anything while his work order was being processed. We thanked him for his understanding and hung up. Fast forward 2 months now (Canceled in Oct 2024) and we are getting calls and emails from a collection company on behalf of Xfinity! For $700!! I reach out to them to help resolve this "oops" as I have everything including chat sessions saved. And they offer no help, sorry all I can tell you is that you owe us this $. "We cannot go back into your account notes because your account is closed." Just crooked and wrong. I have filed a complaint with the FTC and will continue to let everyone I can know what kind of company comcast/xfinity is.