Incorrect contract billing

I got a call on 8 Jan 2015 to find out if I wanted to upgrade my contract. I told the salesman that I wanted to go onto a top up 200. He confirmed he would activate it immediately and my bill each month is only R200. He also confirmed my delivery address to send me a Samsung Galaxy fame. I have never received my phone and my bill has been over R400 each month. I don't know what option this person put me on. After several attempts to get hold of the person who contacted me, I am still unable to get this problem fixed and no one can confirm who the person responsible is for my incorrect billing. I did not agree to this contract that I'm being charged for and I want this fixed.