Debit more than outstanding balance

From 23/07 I have paid in an extra R18000 on my AVAF account excl the usual debit order on the 28/07. The balance outstanding was less than the monthly debit order. Come 28/08 the full debit is processed and there is no notification that I will be reimbursed any amount. Is Absa saying its a coincidence that the final balance was exactly equal to the last debit order? I called AVAF this morning and just before getting disconnected, was told everything was in order. I find there is constant disconnection with your operators and they do not call back. Absolutely annoying as I have to repeat the entire issue again and I have been through this more than once I also received this text on 03/09 "Your AVAF settlement amount on acc *** is R575.92- on condition we receive this amount by ***8. Refer to your settlement letter for T&C."