Blocking a contact keeps them from texting any of your numbers. It works just like it would work on your phone to block a person.
From the HUB Inbox
Click Search (magnifying glass icon, blue circle).
In the Search Bar, search for the contact by typing in their name or phone number.
Select the contact you wish to block.
If you have "duplicate contacts", you may need to click "edit" to edit the contact before you can continue on the next step.
Click More (3 vertical dots, blue arrow). A dropdown menu will appear. Click on Block.
For instructions on how to do this from the inbox (legacy) or the contacts page, click HERE.