Bad customer service

So I app**** for a cellphone contract via Mondo and filledin the paperwork and selected the debit date. Then come the 25th March 2021,they decided to debit on that day instead on the last day of every month. So I call and explain, they say they see that I said last day of every month and they don't know why it went off on the 25th. So I received my bill yesterday stating that my bill for this month is R750, I immediately called in asking why R750 and not R548. 03. Then Ms Natasha Ansah due to the fact that there was no money my account and came back unpaid on the 25th March 2021,I am being penalized R200 due to their fault. So I told I am reusing to pay penalties for their mistakes, she then tells me with a strong tone of voice you just have to pay and can't refuse. I then ask to speak to her manager and she tells me the manager is buay, also the Manager will tell me the same thing. She then tells me to hold the line and gets back to me, she tells me call 10213 to find out what my contract says of when my debit date is it. I ask her last night can I call now she says politely yes Sir, I call the number and that department are closed because it's not their normal business hours, so I am left furious because lady thinks that she can take the customer for a fool by sending them on a while goose chase. I am really ****ed at Telkom, people told me they were bad but I refused to listen. Well lesson learned, now I will have to ride out this contract but then I am done with them