Bought new iphone 4 with out contract now can't get service on it at all?

I got a new iphone with out a contract bc mine broke to the point of no use i put my sim card in it and loaded everything to it and it does not have service. What is going on and how can i get service now.

Added (1). Had it plunged up to laptop and went into iturnes it updated and everything i'm not understand y its not working maybe tell me how or what you mean by check to see if i used itunes bc i think i used it.

Check your settings and make sure you have plugged your phone into iTunes to activate it.