MTN is ripping me off

I have never been this angry with MTN. The poor customer service I received from Simmy who works at the Cresta branch was ********* and disappointing. She wasn't helpful, she wasn't very clear and couldn't resolve any of my problems. She was actually very dismissive. My phone has been off since Saturday 30th January, at first I thought that it was a network issue but apparently my phone has been switched off because I have an outstanding amount of a ridiculous R10000, this is absurd because I opened my contract in October 2020 and my package is R499 but it turns out that I owe R10000 in a period of 4 months (HOW). I am being told that I have been moved from debit to cash payment but there was no communication in this regard. MTN needs to open my line ASAP, I cant even call their customer care with my phone. How on earth am I going to be assisted???