← Area code 406
406-489 phone numbers
Numbers 406-489-0000 to 406-489-9999 are assigned to New Cingular Wireless PCS, LLC in Sidney, MT. 4 of its ten thousand-number blocks are assigned to other carriers (number pooling).
Not assigned to any carrier: 406-489-4xxx, 406-489-6xxx — calls from these use spoofed caller IDs.
Source: North American Numbering Plan Administrator, Nov 3, 2026. Numbers can move between carriers.