Cjange of banking details

I did change all 3 my MTN contracts banking details on 13 Aug witrh reference ***<br> At the end of Aug only one of the three contract were debited correctly. They debit the other two to the old account which occur R120 bankcosts for an account without available funds. I did phone the dealership at Central ave Flamwood Klerksdorp and they told me that they did change it on all my accounts. To day after one month they debit the one account correctly and the other to to the wrong account which occur another bankings costs of R120-00 for an account with unficient funds with an amount of the 2 months. This morning I receive another referance number *** You cannot get through by phone and I want this to be sort out today as well as the credit on my account for the uneccasry bankcosts. I think their billing is pathetic because the agent got all the documents that the changes were made correctly and in time but MTN still bill wrong.