Why is my iphone 4 being like this?

I just got a new iPhone 4 and it was working before my dad gave it to me because he called me to check if it worked and than when I received it, and than I couldn't call and receive calls from other people and than I tried signing up for the app store and than it said I needed a credit card to register with (which was weird because I though the app store was for free ). How do I sign up for the app store for free and how do i make my phone able to call and receive calls from others?

You have to have a credit card to sign up for the app store but it won't charge you so long as you don't buy anything. If you download iTunes on a computer then I don't think you need a credit card to sign up. ITunes does ask for a lot of information.

I'm not sure why you can't receive or make calls. Wherever you got it from you should take it back and show them the problem. They will probably give you a new one if it's broken. It may however just be your simple or your network. Try putting another simple card in and see if it works.