Wrongly Billed for a year

I have been billed R311.70 for which I did not signed for. I went to the Vodacom Shop where I signed the contract and the manager called the representative who helped me. She said she don’t know what it is for but I signed for it so its part of my contract. She also said its the first time she see something like that. I have addressed this issue from the beginning of my contract with vodacom but they couldn’t assist. They said it was for some insurance, but I told them I have my own insurance. After I googles what this New Year every band is, I discovered I signed to get a new handset every year. Which I don't want. Even after I checked my upgrade date its still within a year. So I really don’t know whats going on.