By default numbers not in your contacts are blocked.

Optionally allow:

• Numbers you have contacted
• Numbers within the selected groups
• X registered call(s) from the same number within a set amount of minutes
• Numbers found in messages
• and more..

If the app rejects calls from contacts on Android 10, allow Contacts permission manually in App info → Permissions.

• CALL_SCREENING - block or allow call
• READ_CALL_LOG - check you have called the number and count times the number have called you in X minutes
• READ_SMS - check you have sent a message to the number and you received a message from the number
• NOTIFICATION_LISTENER - find mobile numbers in incoming messages
• READ_PHONE_STATE - check on which SIM the number is calling
• RECEIVE_BOOT_COMPLETED - persist clean expired numbers job across reboots
• READ_CONTACTS - check the number exists in contacts on Android 10 or block calls from them