Arrears after cancellation and final payment

In October of last year, I went in to my local Telkom branch (Potchefstroom) and said I wanted to cancel my ADSL line, and gave the instruction to do so. At the beginning of December I went back to the branch to pay and make sure that everything had been taken care of. The lady assured me that my line was cancelled and that this was my final payment, I asked several times to make absolutely sure there was no confusion for either of us. Now, having never receiving anything from Telkom since then (Bills or correspondence of any sort) I get an sms saying that I have been \handed over". The same lady at my branch now tells me that 'the system' says I owe the money. When asked what for"