Empty promises and poor service

Hi my name is Betty Sephaladi I'm writing this with my heart bleeding and very huge disappointment about the service I received from cell c I had several contracts with them but in all of them I don't usually reach the contract term I always settle them early, I called them to ask for a settlement amount which they gave me I paid the amount including the premium for the current month and I went to their client service to ask for a paid up letter boooooom cell c are telling me I still owe another amount for what I don't know and this is not for the first time doing this to me and the last time I promised myself I will never go back and take another contract with them but to my surprise I still went back to them, but this time I am not going back to them until they fix this I'm not going to pay any single amount they must just fix thier issue and give me a paid up letter that's it.