Just adhere to these instructions.

Some carriers may include a different app for messaging.

You would have to use an app like SwiftReply, mentioned below.

SwiftReply Turn auto-reply on

If your messaging app does not offer a Blacklist option, use Handcent.

Now all of the text messages from that person will be blocked and not visible in the Handcent app.

You wont get notifications youve received a message from the person either.

Some users have reported that the app Private Space works well for them.

I recommendSMS Auto Reply.

The app will allow you to setup an auto reply for specific Contacts.