If you block someone, you will be able to send messages to, but not receive messages from, that person.
If you are blocked by someone, you will not be able to send messages to the person who blocked you, even though you can receive messages from that person.
You can block a contact or unblock a contact, by following these steps:
- Go to the Inbox and open the conversation thread you have with the contact
- Tap the contacts name or phone number at the top middle of the screen
- Scroll down and click "Block" or "Unblock"
If you are blocked, the person who blocked you is the only one able to remove you from their blocked list.