Vodacom Fibre deal gone wrong

I have cancelled contract for the fibre by them because i was suppos to pay R599 for and i got bills for 3 months saying i owe them R1259 which is rediculious as i dont have that money to pay. I try getting their customer service on the phone if im not on hold i cant get through to someone to help me because i cant g phisically to the shop. How can i apply for a pamnet plan or anything as this is messing up my credit score?