False ******** Advertising

Last year October Cell C called and offered me a data package for the amount of R138 per month for the duration of 24 months which I accepted. the agent advised that I could terminate the subscription at any given time with no extra costs. The first deduction via debit order was for pro-rata and the second was for R845.45 and the third one for R1575 which I clearly don't understand. I've logged a call disputing the deductions and the subscription, but they cant seem to resolve the issue. How is it possible that you sign up for one thing and end up paying so much for a data bundle that was agreed upon for R138 /p/m