Telkom - poor service

Telkom's service is just plain poor. I received a bill - suddenly I have added expenses - which no one seems to be able to explain. From a bill of just under R600 for 20MB line (a promotion I agreed to) - I received a bill over over R900 - how? We struggle with the wifi - sometimes it's good, sometimes it's so poor - and this is the fiber option. I think when my contact is up, it's time to move on!