ADT not giving you what is promised

My Mum signed a new contract with Cameron Govender. He promised that 3 months would be free and the first premium would go off on the 01 Dec 2018 and he sent me an email to confirm that an error was made on the contract and he assures me it will go off on the 01 Dec 2018. The first premium went off on the 01 November. I called Cameron and again he assured me that the accounts department has resolved this error and December premium will not be debited.....and it was!!!! It is getting extremely frustrating dealing with ADT and this back and forth promises that doesn't materialize.