Contract problem with MTN

I had a contract with MTN Hazyview and I paid fully and now I want to open another contract of a slim card data and I'm unable to as they said they owe me 80c mind you I don't owe them they owe me, somehow they are telling me I should go to the shop to close the contract, I went they didn't help me and told me to call, I did they did not help me and they always refer me to their shop in which they did not help me. Hello Peter please help me. I need a phone for work..