debit after contract ended and confirmed ast debit

[I have been with telkom from the begining of contract until the end of it without a problem and it end on 02/07/2021 and they made their last debit on 25/07/2021 and they confirmed it from their social media platform but the following month things were not good because they debited a amount of R301-70 and when I ask about this debit,they didn't answer/feedback about it and I have reversed their debit two days ago and also blocked them until I get feedback about that R301-70 and I want to know what is it for?