603-259 phone numbers

Numbers 603-259-0000 to 603-259-9999 are assigned to Level 3 Communications, LLC in Littleton, NH. 7 of its ten thousand-number blocks are assigned to other carriers (number pooling).

Not assigned to any carrier: 603-259-9xxx — calls from these use spoofed caller IDs.

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

Reported numbers in 603-259