24 month contract now on the third year

I had a contract with Vodacom which ended 2014 October, I contacted Vodacom on time and was advised what I needed to do. I had two numbers on this contract and only one was converted to prepaid. 30 months later no one could give me answered after numerous calls and queries, contract dept refers me to prepaid who inform me I need to go back to the contract depr as they cannot assist. To date about 34 months later no one in Vodacom is prepared to help nor give me responses, I keep on being transferred form pillar to post and each department refers me to the other. To make matters worse this account keeps on being billed and this account has been handed over to a collections dept for their own error. I never agreed to a contract longer than 24 months and I need answers. Why can no one assist me and why do I keep on being billed? Why have I been told over and over that my number is prepaid but I keep on being charged. What am I being billed for? Why was I not made aware that the contract is longer than 24 months. I need answers ASAP or I will be reding this to the CEO and Ombudman.