False information

2 months back i signed a contract with Cartrack and i was told that they will start debiting from the 25th. on the 27 April i called them to let them know that there was no debit from them and the consultant told me that it has been deducted. the following month the same thing happened and i was told the same story. then i received a call from them telling me that they made a mistake they were deducting from someone else's account and the owner of the account decided to reverse the money. i am now in arrears for something that i did not do, they used a different account number and i'm to blame and they expect me to pay R500 but the service was never delivered and it was not our agreement that i will pay R500. to-date i only receive SMS's that i'm in default but i gave them my bank account number. no 1 contacted me to rectify their mistake. your assistance will be highly appreciated *** R501.05