Telkom robs me

Every month telkom does not debit my account, or they debit my account after like 4 to 5 months but they claim they are debiting every month. I do not get any sms on my phone by the 31st so I pay my installments cash . So I've become a custom to this so all of a sudden they said they debited my account and they were no money in my account and they charged me an additional R250 . This is not the first time it's happening. I've phone the custom care numerous of times and they said that they set my installments date right but they do not debit it so I have to withdraw the money and pay cash every month , then they phone me to say I owe them money because of failing to pay on time and I have to pay additional fees . This is unfair and is happening on a regular bases . They accounts department does nothing about it and I have to wait like 3 to 4 weeks for feedback yet I pay on time and they cut my data and contract plan for the time . I hope it changes soon .