vodacom bad service

I took a contract phone with vodacom and the sales consultant did not tell me that am on an open line which i would not agree on. so they kept billing me and only after 2 months do they tell me my account owes 1000. i asked called them and asked them to listen to the call between the sales agent and me and they said they cannot remove the amount so if i want to query i must speak with the sales consultant who sold me the contract, they transferred me but he is never at work. they never get back to me as well. i do not think its fair that i pay because there is no full disclosure and the its not treating customer fairly