Outstanding amount on my account

In m March this year I took out a contract with Cell C every month I paid the contract according to the statement they send me then in June I took one out for my wife they said that I would have to pay extra the end of Jully for the prorata usage for June with was not a problem the in Jully I paid the amount due on the statement I changed my debit order date as I only got paid by the 4th of every month then on 4 September 2023 I received a statement with amount payable R797.98 and on 6 September 2023 thy tried to take an amount of R867.98 in my bank account was only enough to cover the amount of R797.98 the R867.98 was rejected and on the same day the took an amount of R797.98 from my bank the R867.98 stayed on my cell statement and now the barred my account because of the amount of R867.98 another problem is that my debit order date is the 6th of every month but Cell C will put a debit order through any time of the month the want to charge me R70 as a penalty for debit order not going through now I want to know why must I pay for a mistake on their side and for people that clearly don't do their work.