Incorrect Bill Every Month

I am fed up with Telkom billing system. For the past 5 months I have been receiving incorrect bill & I have to query what is it for. There's no explanation & all they do is just to credit my account. I am tired of having to call every month so that my account can be fixed. I am tired of your incompetence. One of my contracts is expiring in few days time & I wont be renewing it & the next one is due in April 2016. Please rest assured that you will never ever hear from me. The remaining two will be cancelled as well, I cannot wait until it expires. I'm certain I deserve better than this ****py service you have been giving me