Top up changed to open account without permission

My 2Gig top contract was migrated in August to an open account by Vodacom person without my permission. A contract is a legal binding document between a seller and buyer. I have logged various disputes via telephone and emails. I have received a bill of R6000 on a R278.00 contract.. Despite all phone calls been made, emails been send on which sometimes I had a call from Vodacom, explaining the dispute over and over, nothing is been done. I requested Vodacom various times please correct this contract to the 2GB top up what it was, and they kept changing it to incorrect contract. I have paid my normal contract fees on my account, on which I have 5 lines, (all of them top up) which Vodacom now suspended all my lines due to their mistake..