Open a conversation with the person you want to block. Tap their name at the top of the conversation. Scroll down and tap Block. Tap next to Block Messages. read more
If you and the person you block are in a group conversation together, you'll be notified before you enter the conversation. If you choose to enter a group conversation with the person you blocked, you'll able to see their messages and they'll be able to see yours in that conversation. read more
Hi Matthew, If you don't want to block or unfriend someone, you might consider moving your conversation to your "other" folder where you can review the messages when you want to. read more