VERY BAD SERVICE FROM VODACOM

I have been trying to cancel a contract with Vodacom since the end of May, when I call in the agent tells me someone will call me back and they never do, on the 1st of July my bank account was debited with almost R500, when I called in, once again someone was going to call me back and I'm still waiting, when I called in the 1st time, I was told that my contract would be cancelled, only to find out today that this was never done and I'm being billed every month. My contract was due for an upgrade in March already and still battling to get it cancelled.