Accounnt cancellation

I cancelled my account in August and was told it takes 30 days for the cancellation to take effect. To my surprise I am still being invoiced for a contract that was supposed to have expired end of July. I have filled in cancellation forms, visited Telkom stores and called their call center to no avail. This is chocking considering I am being charged amount higher than what I was paying when my contract was in force. This service is **********.