Can't SMS With Your iPhone 4S?

Do you have a problem with your iPhone 4S sending messaging? One of my buddy he called me asked me why his new iPhone 4S cannot sending SMS. Tell you true true one... I'm not a Apple's wiki but I do my best to know why and solve the problem of it. I looking in the net also can't find if until my friend he show me this note on the top. Just sharing this info to you guys if next time you or your friends having the same problem like my buddy do!!!!