How to block people on iPhone?

I have an AT&T iPhone 4S with iOS 5.1.1, and I have this number I don't want calling or texting me. Is there a way to make it so I ONLY get phone calls and texts from my contacts? Or if there's a way to block certain numbers that would be cool. And if I block them, would I myself still be able to text them?

There's a way to block certain numbers from calling/texting you, but it isn't done on the iPhone itself. That is a $5.00 x Month feature offered through AT&T. Call them and inquire about Call-Blocking if you're interested and willing to pay for it.