Cancellation of account

I cancelled my ADSL line with Telkom online as requested and I am still being billed and charged interest 3 months later. I went online to cancel my landline account too due to not having service for the past 3 weeks (****** cables not being replaced) but because of the "overdue" amount still in the account , I am unable to cancel online. When calling the contact centre, they acknowledge that the ADSL has been cancelled and yet still being billed?