1. From the home screen, select the Messages app.
2. Select the desired message thread, then select the Contact at the top of the screen to get the Contact options.
3. Select Info.
4. Scroll to and select Block this Caller, then select Block Contact to confirm.
From the desired contact, scroll to and select Unblock this Caller.
From the home screen, select the Settings app > scroll to and select Messages > Blocked Contacts.
Note: You can also access blocked numbers and contacts by selecting the  Settings > scroll to and select Phone > Blocked Contacts or  Settings app > scroll to and select FaceTime > Blocked Contacts. Learn more from the Apple support article Block calls and block or filter messages on your iPhone.
From the Messages screen, scroll to and select the  Filter Unknown Senders switch.Â
Note: In the Messages app, Filtered iMessages will be routed to a separate tab. You will not receive notifications for Filtered Messages. Learn more from the Apple support article Block calls and block or filter messages on your iPhone.