Unhappy Customer- Unfair and Incorrect Billing!

I had a contract with Vodacom, which came to an end in June 2017. I was told that I needed to cancel my contract a month before the contract ends which was in May 2017. I called in to cancel only to receive clear confirmation after my third attempt saying that is has been cancelled. Months later in October I received a statement with a Zero balance. Vodacom has been calling my family and friends saying that my account is in arrears. They literally went through my call log calling my close friends looking for me, telling them my Vodacom account is in arrears and I need to pay urgently. First of all, they have no right going through my call log and calling my family and friends, disclosing important information which is not even true. I am disgusted. I called them and they saying I never called in to cancel but i specifically know I cancelled my contract in May. I told them since all of your calls are being recorded go back and check in May that I did indeed call. I am disgusted in this service because they could not find anything and are telling me now that my contract is in arrears because I only cancelled in September. I cancelled in May so please go back to your call records and check. Please provide feedback urgently because when I call the customer service agents cannot provide proper feedback the service of Vodacom is unacceptable and I would not advise anyone to take out a contract with Vodacom!!!