Charging for a service I expressly did not want

Last year I called Telkom to cancel my internet service, but to keep my ADSL line. They told me it would be R299 a month for a 4mbps line rental. Except my invoices have been coming in at over R500 a month, because they're including an Evening W/Ender plan that I did NOT ask for - nor do I have any use for! I told them over and over I only want data - NOT voice! I don't even own a handset - nor do I want to! I have left several Call Me Backs on their website (after waiting hours for a consultant to become available on their chat to us service!) - but as yet, no call. Come on Telkom - stop trying to milk me for more than I'm prepared to give. This isn't cool.