Happy to hear I'm not the only one.
7 years ago 3 offered me a contract, I accepted. O2 then offered me a miles better deal, so I cancelled with 3. They informed me the cancellation had been completed. A few days later, a phone comes through the post from 3. I phoned them to ask where I send it back and they said I couldn't as I had taken the contract. I explained, they refused. I said in that case, I'll cancel now as I am still with 14 days. Brick wall. I phoned every day and got nowhere. I cancelled the standing order they set up with my bank but just couldn't get it through to them I wanted to cancel. Suddenly, on the 15th day, "Yes of course you can cancel sir, that'll be £570." I refused, stating that I had not actually signed anything and they even tried to say my mum signing for reciept of the parcel was a signature of contract.
7 years on and I'm still getting letters from debt recovery. Every time, I ask them to send me the contract paperwork and I will gladly assist, failing that, I ask you to please take me to court. Please!
Have actually been tempted to threaten action against them in the past.