Extra billing on my account

I've never been this frustrated Telkom sales agent called me last year, selling me a simcard that had 25gig for R85.00 I took it since Kgotso needs data for homework and assignments. December they charged me extra R700 after I specifically told the lady to cancel anything extra on it. This month they charged me R500 extra. I was on my phone calling them for atleast 2 hours mara I'm not winning. I decided to cancel it. Im defeated. Sales department and billing department have been giving me the run arounds. It looks like no department is taking any responsibility.