Billed for non use

I emigrated to the Cayman Islands on 1 January 2015. I cancelled my telkom account on 11 December 2014 (after giving a months notice). The operator ensured me all the services will be cancelled, however I am still invoiced on a monthly basis for the line rental and adsl rental and am being charged interest as the \outstanding amount"is not paid. I don't even use the service or live in South Africa anymore as mentioned numerous times on the emails and calls made"