Can't give notice

Hi have been trying for the last 2 weeks to give notice of cancelation of my contract.

The number supp**** don't even ring and I registered on telkom even there I keep being cut off so I can't process my notice.

How am I suppose to cancel as they need 21 days before expiry of contract that you give them notice.

Now I am past the notice date. And my account will be debited again.