Vodacom not wanting to cancel my contract

I called vodacom in December last year to cancel a contract and it was not canceled. I called last week and ask why is it still not called the consultant said she is logging a call with the manager of the person that canceled it before and I will get a refund. This was not done. I have called 2 more times after that and it's still not canceled. Please let me know what I must do to get this contract canceled