A friend of mine signed up to one of these doorstep salesman peddling cheaper gas if you moved to with them.
Subsequently he changed his mind and cancelled it. Thought no more until he realised that he wasn't getting a gas bill. Prospective company had cancelled old contract but never re-instated it. Calls to both companies who both denied being the supplier and despite several attempts, no one would take it on because there was no one to transfer it from.
Years later, he still gets 'free' gas.
He really did try but ended up banging his head against a brick wall. Now he doesn't worry about it.