Problems with Oyster Auto Top Up

Anybody know how to deal wthTfL on this one. If I haven't done something how do I prove that I didn't do what I didn't do.

I had problems cancelling an auto top up 3 months ago but the ticket office at Heathrow suggested issuing a new card with a new number. So I got a completely new Oyster card and they transferred the credits onto it from the old one.

Used the card in January and again on Tuesday and TfL have again done an auto top up and tried to recover £20 from a non existant credit card. Called them this morning and they are adamant I set up an auto top up in June 2012 on a card that I got in January 2013. They said that unless I can prove that I didn't set up the auto top up then there was nothing that they could do.

Should these people really be allowed to run the underground in London.