Frustrated and angry client - no service from Vodacom

Vodacom gives extremely BAD services. End of April I cancelled my data contract. My contract was never cancelled. Since the end of April until now I have made a number of phone calls, gone into 2 different branches. I get lots of promises but NEVER DOES the job get done. By now I should have lots of emails but have not received one. You can never hold person responsible because even though you have their name you can never get back to them on the phone. When asking for that person by name, no one knows who it is. Vodacom never phones you back.