https://support.google.com/phoneapp/answer/6325463
Block or unblock a phone number
If you don’t want to get calls from a certain phone number, you can block it. When the number tries to call you, your phone declines the call automatically.
Important: Some of these steps only work on Android 6.0 and up. Learn how to check your Android version.
Block a number
- Open your Phone app .
- Tap More Call history .
- Tap a call from the number you want to block.
- Tap Block / report spam.
Tip: If visual voicemail is on, blocked callers cannot leave voicemails. Learn how to turn on visual voicemail.
Block unknown numbers
- Open your Phone app .
- Tap More .
- Tap Settings Blocked numbers.
- Turn on Unknown.
This will block calls from private or unidentified numbers. You will still receive calls from phone numbers that are not stored in your contacts.
Unblock a number
- Open your Phone app .
- Tap More .
- Tap Settings Blocked numbers.
- Next to the number you want to unblock, tap Clear Unblock.
Tip: Any calls you got from the number while it was blocked won’t show in your call history.