Pathetic customer service

Supersonic bills me R0.00 rand on my fibre line for 5 months and 2 days after i log a call for my line that broke they send me an sms stating my account is behind and tell me to pay 5000 rand or else my serv8ce will be suspended. Phoned in 6 times already and cannot even speak to a manager she is always busy or unavailable or on lunch. Im on a month to month contract they should have picked up after the first month that there is a mistake with the billing so how is this my problem. The service is absolutely pathetic. After i query the sms then they want to send me an updated statement that shows outstanding amount unbelievable