Double Debit and Poor Customer Service

I paid the outstanding fee to Cell C by 31st of May 2021 and at the time my commitment value was R1702.13 and I paid the fill amount after calling their call center to confirm that if I pay the full amount they will no longer debit my account because it is fully paid up, but today Cell C is still debiting my account and they are failing to explain why I have called and the agents are giving me u8nreasonable explanations.

One Agent made fun of me thinking that I do not understand EFT and Debit I guess they are more educated than us as their clients.