831-307 phone numbers

Numbers 831-307-0000 to 831-307-9999 are assigned to Level 3 Communications, LLC (rate centre CASTROVL, CA, NANPA abbreviation). 1 of its ten thousand-number blocks are assigned to other carriers (number pooling).

Not assigned to any carrier: 831-307-3xxx, 831-307-4xxx, 831-307-5xxx, 831-307-6xxx, 831-307-7xxx, 831-307-8xxx, 831-307-9xxx — calls from these use spoofed caller IDs.

Source: North American Numbering Plan Administrator, Nov 3, 2026. Numbers can move between carriers.

Reported numbers in 831-307