Incorrect Debit Details by External Sales Company

My contract was opened telephonically by an external sales company, cannot remember their name but they were doing sales on be halve of vodacom. A few months down the line, I get a call from vodacom that my account is in arrears, when I looked at my bank statements I realized that the debit date was incorrect to my understanding. I explained this to the customer service vodacom. He said, that it unfortunate but there is nothing he can do to fix the debit date and vodacom will no longer be debiting my account, I will just have to do the payments inside the bank. I said this was extremely inconvenient for me and will not be able to be in the bank at every pay day, and I too feel that this is unfair as the sales person made the mistake with the debit date. He rep**** and said sorry I cannot help you it is what it is and said bye, no interest shown in helping customer right, bad attitude. None the less I had to carry on with the in bank payments of which was very irregular due to my busy schedule. I tried making double payments when i had time for the bank but inevitably I could not always keep up due to time. Now I cannot get a contract due to this. Was also planning to migrate networ