Forced Onto New Plan Just For Trying to Return Cable Boxes

We started using a Roku for streaming the Xfinity television channels, so we no longer needed the cable boxes we were paying $20 a month for. We went to return the cable boxes and were told (after they took the boxes) that we would have to call and get a new plan for some reason, just to remove the cable box charges from our bill. My husband called and the person completely misunderstood what he was asking to do and she cancelled the whole television plan. So the next day my husband went to the store to meet with someone in person, explained what happened, and was told that our plan was "no longer available" and we were put on a new plan that is the same cost as the old plan WITH the cost of the rented cable boxes! We were trying to save $20 a month and instead got put on some new plan and will save nothing. This was very underhanded and was due to the incompetence of the person we first spoke to both at the store when we dropped off the boxes and when we called. I called this morning and was told there was nothing they could do and they gave us a $20 one-time credit on the bill. This is not a solution to what we were trying to accomplish.