How to block a number on an iPhone 4S?

My brother has a 4S and he's getting weird texts I have heard that there is a way to block a number please don't answer if you are going to say its not possible it is trust me I know people who can I just don't talk to them much but they have done it anyways how do you do it! My brother is starting to get agitated.

Without jailbreaking there isn't a way to block a single or specific incoming number.
There are certain apps which claim to do it though.
The only REAL solution is to contact your carrier & ask them to blcok the number.