Nightmare of my life Telkom

I have a contract with Telkom. My monthly installment is R349. The problem started when they were supposed to deduct the money on the 5th of February 2020 and they reversed the money back to my account. The debit date that I chose is the 5th of each month, from then they started deducting the installment on the 1st of and every month when there are no funds on the account and charge me R202 penalty fee. I went to the branch no one assisted they told me to contact the billing department. They asked me to send the bank statement, l sent it but they still charged me. This has been happening since then, now I have to pay R552 monthly for their incompetence and bad service. I have opted to use EFT on the last day of the month but still their systems don't pick up that I have paid and charge me penalty fee again. Last week Friday the 28th of August paid R650 via EFT today on the 1st of September they block their services where as I have never missed any payments and I have been paying the penalty fees they have been charging me. It seems this is their money making scheme to rip peoples money. And I believe they have listed me because of being a slow payer, they send me threatening messages in the middle night, when I'm payin every month including the extra charges. They really want to tarnish my image and get me blacklisted for their own doing. I regret to the day I took up this contract only if I have known. I never recommend Telkom to anyone bad service it's like every consultant of theirs has been trained not to help a client with issues with them.