A friend of mine that has an android phone through sprint needed to block someone from texting him. So here's an easy way to do it. Only works with a sprint service.

Send a text to 9999: in the message type BLOCK fallowed by the number you want to block. Exp. BLOCK ##########

To unblock a number send ALLOW ########## to 9999

Sprint will text you a confirmation text with each action. Just thought if pass this along.