Vodacom - Shocking service. No response to instructions to cancel contracts.

I have been trying to cancel 3 x data contracts for approx. 3 months. I am told that the numbers are registered on their old system. I have been alternatively told that the numbers will be cancelled or when I phone to ask to speak to a supervisor am informed that the supervisor will call me back. This never happens. What shocking service. Perhaps time to migrate to a competitor when my contract expires in the new year!!!