Vodacom contract

I am deeply sad by the way Vodacom SA treat their customers, On the first of May I cancelled my contracts with them since they had expired, however, they comtinued to charge me, I have trying to call them but they transfer me from one department to the next, they are blaming each other without assisting me, their consultants said they are escalating the matter but they keep on dropping calls and not get back to me. This is not good for my credit record since it displayed as an account in errears