Telkom Expects me to pay for a landlines that I canceled more than a year ago and still get billed for

Telkom sent me an invoice after nearly a year, for a fixed line I canceled more than a year ago. They now refuse to cancel the line because I supposedly owe more than R1800. The line hasn't been in use for more than a year, and I haven't paid for it bacuase it wascancelled, and yet no one contacted me to ask why I'm not paying... The line should be canceled.