Disappointed customer of Telkom

I am disgusted with this company, i was in a contract with this company for two years and not once did my debit order bounce. My contract has now ended in November last year and I'm currently on a month to month basis. This is the first time my debit order bounced back in my account due to not having enough funds (salary decrease due to covid). I had the cash and went and paid my account. I received my invoice for payment for January and saw i was charged for the bounce back of the debit order. Now i was already charged by my bank for the debit order and Telkom feels that they can charge me as well when they were paid for the service via cash and they also don't accept no debit order arrangement as its mandatory as i was told by a customer service representative. Im so angry and disgusted and will be moving to another service provider.