Vodacom charges on canceled accounts

After along time vodacom not telling me how much I need to pay to cancel, they told and sent me the form. I filled in the form went where they were in Walmer Park, paid the amount and submitted the form. I was told it's sorted.

Now they keep sending me invoices after I've canceled. It's up to R2556, 88 on an account that's canceled.

How do they continue to charge when the account has already been canceled?

When you call you only get machines, no person to talk to who can resolve the issue.