Contract cancelled still being billed

I have cancelled my contract with vodacom and switched to prepaid. Looooong story in a nut shell I'm over the drama. However I have now been sent an SMS welcoming me to the package I just cancelled. Attempts to phone vodacom to sort out lead to voice recognition password. This is a flawed concept, and I do not wish to be a part of it as it has caused endless problems on another vodacom number. I would appreciate it if someone could contact me from your office as I am not able to contact you.