No proper info given

I bought the game World of warcraft from BT Games The Glen on 2015/09/12 and wasn't told by the sales person that the game is only a 30 day trail and that I have to buy a 60 day game card which is R500 every 60 days. All he told me is to check if the game will work on my pc. I only came to realise that I have to pay more money to play the game when I installed the game, I went back to them to swop the game for another and was told \ sorry we can't swop the game as it has been opened"how is a customer to know these things if they not being told???? Now I have a game that I can do nothing with. If I was told I need the game card I would have not bought the game. BT Games need to train their staff which they clearly not. That's what you call bad service. """