Poor customer service

I regret taking out a cellphone contract with vodacom, they are billing me for two cellphone insurances at the same time after i tried several times to indicate to them that i have cancelled the insurance, when i called in again regarding this matter i was told that my details are nowhere to be found on the system yet they billed me twice for an insurance of a person who does not appear on their system. I have send them email after email but they are not getting back to me. In the mean time i have to pay this unfair amount. I'm not happy at all with vodaom