Open the Messages app
Select the conversation from the sender
Tap the contact name or number at the top
Tap Info
Scroll down and tap Block this Caller
Confirm the block
On iPhone
Open Settings
Tap Messages
Tap Blocked Contacts
Tap Add New
Select the contact to block
On Android
Open the Messages app
Open the conversation
Tap the three dots menu
Tap Block number or Block contact
Confirm the block
On Android
Open the Phone app
Tap Recents or Contacts
Select the number
Tap Block or Block/report spam
Contact your carrier
Ask about text blocking services
Enable spam filtering if available
Use a third-party spam blocking app
Add the sender to the app’s block list