Vodacom keeps deducting my account even after paying my account off

I had a cellphone contract with Vodacom. And I closed it prematurely. I called them and asked for the settlement amount and early closure fees. They sent me a statement with the amount. I immediately settled the account and sent proof of payment. They even changed the number to prepaid the following day. Now they keep taking money from my account. When I called to inquire no valid reason is given to me. I have to keep reversing debit orders every month and I am being charged by the bank. The floor manager promised to call me and clarify this issue but never did. So frustrating, all these telecommunications companies are the same. We work had for our money so it to be used on bank charges