Non existing help department

Trying to get hold of the call center is nearly impossible and if you get hold of someone they put you through to another department and get cut off. I cancelled my fibre and returned the router to their office, got the slip and reference number and now they tell me they did not receive it from an automated machine and will bill me R3000, how do one get hold of someone who can assist you with this company??????????? I am so frustrated.....................