Handing debt over for money not owed

In Aug 2016 I asked for my contract to be terminated. I struggled to get a response. Eventually I spoke to someone who said I can leave the device in the property as we had sold the house as we now own the device. Months after we moved out I got a phone call saying we need to pay for the device or they want it back. I told them I have no access to the property anymore and they are welcome to go and fetch it. I said if they can show me a contract where I agreed to return the device or pay for it then I would continue these discussions further. At this points however, I feel like I am being ******ed for this money. I have now been handed over to a debt company for money I don't owe. Nobody can help me!