VODACOM DOES NOT WANT TO CANCEL MY CONTRACT

I have been wanting to cancel my vodacom contract since last year October. The consultants say that it has been cancelled but every month I still get the airtime that I was receiving from them. It's been 4 months now and still nothing. Every time I call to cancel they say it has been cancelled but I still receive my airtime. Like I do not know what to do. Please help!!!