Contract problems

I was a client of Cell C for more than 15 years and everything was okay until I took a second contract last year (2021) July/August. They have a debit order problem for two to three month and to my surprise my service was suspended without any notice and when I made enquiries I was told they couldn't debit my account because of their problems in their system, I had to pay via EFT for the next three month, to my surprise when the next bill comes it shows my account are in areas. I called them and email the proof of payment but still today I couldn't get this problem sorted out, they insist I am owing them and the money keep escalating each month.