You can block a contact from texting you by using the block feature. We warn users not to use this feature because it also opts the contact out from receiving texts in the future unless they opt back in themselves from their phone.
There are two ways to block a contact:
Go To Contacts
At the bottom of the page, select Blocked Contacts
On the next page, enter the phone number you wish to block from being able to text you.
Search for the contact's name or number in the filter at the top of the Contacts page.
Then, click the lock icon to the far right of the Contact.
Important: Clicking this lock will also opt out the contact. If you have mistakenly blocked a contact, unblock them by clicking on the lock icon to the right of their contact and have them text in your keyword.