T-Mobile/Sprint Scam ID and Scam Block: These are the two free anti-robocall tools you'll need to take an extra step to enable on your smartphone. Scam ID tags suspicious calls and Scam Block stops the calls before they ring through to your phone.
To activate Scam ID: Dial #ONI# (#664#) > press the call button.
To turn off Scam ID: Dial (#634#) > press the call button.
To activate Scam Block: Dial #ONB# (#662#) > press the call button.
To turn off Scam Block: Dial (#632#) > press the call button.