Device won't switch on at all? Please help

Bought a new samsung galaxy s2 about a month ago. Have downloaded about 10 apps on it so far. Some apps do contain bugs but the app just closes itself when this happens. Phone itself occasionally restarts itself when this happens. Today it was fully charged. I had been using it throughout the morning but i'd say there was about 70% charge left. It then froze and switched itself off and wouldnt switch on again. I took the battery out and put it back in. Nothing. Connected it to charger. Nothing. It seems as if the battery has lost connection to the actual phone. Very annoyed as this is a new phone. Any help would be helpful.