Overcharged

I'm so not happy with service received from DStv, I was told that if I let them debit my account I will pay less and no-one told me it's a contract, I've been paying R423 suddenly in August R536. 71 was debited on my account and again in September R564. 00 debited, I've been calling to enquire this sudden increase and they kept saying they will reverse it and suddenly I'm being told that it's a contract which was never communicated with me.If can make so many calls to them to enquire I'm sure 1 call wouldn't make a difference to ask them to extend my contract. No transparency, I need this rectify asap, I've calling numerous times for the same issue and the Agents that tried assisting me were nice and one even told me that the "contract" expired on the 1st September but I was already overcharged in August, total ripoff Im telling you.