Why does my Fly slt100 mobile phone not turn on or charge?

I have recently purchased a Virgin Fly slt100 mobile phone and when I first got it I managed to turn it on and have a play with it but after a couple of hours the battery died. As soon as I got home I plugged it into the mains through the battery charger and it started to charge, few minutes later it said it was fully charged but the battery died within a couple of minutes. I decided to plug it back into the charger and now it is not displaying the charging screen or turning on what so ever! Can anyone help me with this problem?Why does my Fly slt100 mobile phone not turn on or charge?WTF take it back to the shop where u got it from