unlock the bicloud verify

i have one iphone 4s and its get icloud verify and thats in the name of the owner ho befor used and i dont have acsses to the owner who i bought the phone from him (shop man) and i use this mobile befor . so help me to onlock that iphone4s bcz i need the data. and my main question is whatis is the way to oonlock my iphone 4s . without finding the last owner? and i dnt know where is he now and they shop also its close