Billed for two handsets

We have had a contract with vodacom for two years. As we were making inquiries about the account we saw on the screen of the lady assisting us that we have been charged for two handsets for the duration of the contract. The extra handset payments would add up to +/- R1400. In trying to sort this our they will not deal with us and are passing us from person to person. I wonder which staff member scored a free Blackberry! :-(