Absolutely horrible

My phone contract expired this year

A few months later I got an sms saying I can upgrade so I went in and checked about that and wanted to renew it and get a new phone. They said it will be a monthly of 500 and continued on the system which she then printed out a form saying it will be R400 then if I pay R6700 now. I asked her why and she said that is money owed and there is no money owed I even showed her my account that nothing was owed and she said she will log a ticket she logged one and it was instantly closed again. I also explained that when I got this number it was a recycled number so it belonged to someone previously and that I should just go in and they will give me a new number which I just left and dealt with the number and people calling me and the sms's of his personal details. I then wanted to rather just cancel this contract and move to a different provider and they said I cannot cancel only after 3 months and yet again just accepted it and moved on. I was without work yes and some payments might have been a bit late, but still everything was paid and never ever was there an amount of R6700. I now do have a incoming salary again and I don't get why I am not allowed to renew or cancel my contract. I just want this to be canceled so that I can move to a new provider that isn't this ***********