1. BLOCK: From the home screen, select the Messaging app. Select the desired message thread. 

step 1

2. Select the Menu icon, then select People & options. 

step 2

3. Select Block. Select OK to confirm. 

step 3

4. UNBLOCK: To remove a number from the Blocked numbers list, from the Messaging app select the Menu icon > Blocked contacts. Select UNBLOCK next to the desired number. 

step 4