Bad treatment from Cell C

I have 2 accounts with CellC- the oher one was expiring on 13/12/2017 and the other one is still new but I want to close it as well. On 18/10/2017 I called CellC to change my banking details and from November they were supposed to start debiting from the new account, but they did not debit the account that I was closing and they debited the other account from my old account. I called them to find out why they are not debiting their money and why they debited the other one from the old account. The only answer you get from CellC everytime is "I am not sure". On 18/11/2017 I was promised that they will resubmit the debit but that was never done and instead the account was suspended. Whose fault is it? Must I force CellC to debit their money? On the last wek of November I was called by CellC and told that the reason why they cannot debit is because there is an error "Desktop invalid and I must go to my bank to find out. I took my time and went to the bank, there is nothing wrong from my bank side, the other companies are debiting my account with no problem, I sent an email to CellC to inform them that there is nothing wrong on my account. On the 15/12 the other companies debited again but not CellC. I am not going to pay any charges for non payment because of their negligence, if a person does not know what to do why cant they ask?

I am so tired of calling and emailing CellC as if it is my full time job. I want both accounts closed with immediate effect and they must take their money with no extra charges and stop inconveniencing me.