bad service

My dad has a vodacom account that i am paying now for 6/8 years. We went to vodacom in cape gate and to vodacom malmesbury giving them letters saying that my dad gives me permission to talk on hes behave because i am the 1 paying it. That was n long time ago. The reason we did that is because my dad is a long distance truck driver and is not home and he is not allowed to answer his phone while driving. So on the 25 of June vodacom deduct money from my bank account and i pay this account via eft every month. I dont no where they got my banking details from and even the amount doesnt make sence, and this acount is not in arrears.. I phoned now coz i want answers and i want my money back. So now vodacom say they cant speak to me and that my dad needs to make time to phone them. I told the gentlement that we did sent letters already but he doesnt want to give me a hearing. I want answers and my money back today or i will take this matter further..