user: Question: What is the On-air ID of FM broadcaster 4NSA?
Columns: ['Callsign', 'Frequency', 'Band', 'On-air ID', 'Purpose']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['4AA', '1026', 'AM', '4MK', 'Commercial']
SQL:

assistant: SELECT "On-air ID" FROM "Table" WHERE "Band" = 'FM' AND "Callsign" = '4NSA';