Vodacom cancelation issue

I've been trying so hard to cancel my contract .Vodafone customer service forces me to continue with it although I've told them on many occasions that I do not require it anymore. They keep me on the fone for hrs trying to convince me to continue. I refuse to continue and they still don't listen and keep debiting from my acc for another 2yrs.Now when I tried to cancel they refuse so I stopped the debit .now they have the legal dept foning me everyday.Whenever I fone to cancel they ask me to go to Vodafone in the mall and when I go there I'm asked to do the cancelation telephonicaly.I am 68yrs old and am tired of running to the mall and spending hrs on the fone.I need help with this problem please.