Telkom is doing ***** on my account .

I opened a contract with Telkom on the 28-11-2014. I signed the papers for my contract and the agreement was that I will pay an amount of R359.00 for 24 months however that changed as Telkom says I have change to a different plan which I never did and I never signed any Documents for that or even agreed on that however they still debiting mu account with an amount of R462.50. They're doing ***** in my account and when I call them know one is will to assist me they keep on making empty promises say they will get back to me and no one those. I want to sue them they have cause me financial stress, time, made me feel like a fool not important. And kept on debiting my account with the amount we never agreed on. Am tired of telkom please tell me how can I sue them cause they have caused me so much stress in my life this has been going on for more than 3 months and know one is helping me I spoke to more than 10 people no assistance. Please help I can't take this anymore...