Add any phone number you don’t want your agents to call or whose calls you don’t want to receive into your blacklist.
You can compile a blacklist of phone number in the web interface, just go to Account > Settings > Blacklist:
Select "Add a number" in the top right corner.
To add a phone number into your blacklist, you need to select the country area code and enter the phone number in its basic format (e.g. 949111222). Then select whether you want to block the number for inbound or outbound calls, or both.
Blacklist will protect you from unsolicited phone calls.