← Area code 520
520-737 phone numbers
Numbers 520-737-0000 to 520-737-9999 are assigned to Allo Communications LLC (rate centre SIERRAVIST, AZ, NANPA abbreviation). 6 of its ten thousand-number blocks are assigned to other carriers (number pooling).
Not assigned to any carrier: 520-737-1xxx, 520-737-2xxx, 520-737-3xxx — calls from these use spoofed caller IDs.
Source: North American Numbering Plan Administrator, Nov 3, 2026. Numbers can move between carriers.