HOW CAN I UNLOCK MY UNACTIVATED IPHONE WITHOUT HAVING TO BUY ANYTHING?

I paid for an Iphone from someone and when i press the round symbol at the bottom, even when i have my simcard in, it asks me to bond my iphone to iTunes. I dont have internet on my phone devise and i wish to keep my phone devise the same price. How can i clear the Iphone but activating it or joining it to iTunes?