Bound to non-existent contract

When I moved house my line was transferred both voice and adsl. When I tried to cancel my adsl I was told I cannot as I just took out a 24 month contract upon moving, which I had not. It tool about 6 months for telkom to realise no contract existed which they charged me for and finally suspended my voice and adsl line due to non-pmt. They are now holding me liable for the full amount and still claiming I signed a contract. Yet the contract cannot be produced. This is not the first time. Previously I paid the amounts due and waited for credits that never came through.