Telkom *****s from us

I have a two year wifi contract with Telkom for R369 a month with a limit of R1 if my data is finished, In May this year I was charged an extra R286 for extra data used. I have sent a query to telkom twice and they keep coming back saying that it is correct. Now how can it be correct if the limit is R1. It must be a technical glitch on their side. I want my money back.