Misrepresentation by Elite Mobile

I received a call in December from someone allegedly from Vodacom, turns out it was actually Elite Mobile. My contract was due for an upgrade, so the consultant sold me a package with 1000 minutes, plus various amounts of data, and then asked if I'd like a modem too, and I said yes. This was supposed to kick off in January. When the modem arrived there was no sim card so I called Vodacom, they said I had been sold a modem contract and that I must remove the sim card from my phone to use in the modem. So how am I supposed to use the minutes? They then told me that it was actually Elite Mobile who had called me. I called Elite Mobile and after a long time on the phone finally managed to get someone to arrange for collection of the modem and cancellation of what they had sold me. Now on my January invoice, as well as my existing contract, I have been charged for 1000 minutes for December (considering the new contract was only due to start in January) and 1000 minutes for January! On calling Vodacom, they told me I must have phoned and asked for these minutes!!