user: Question: What is the Callsign in Brisbane with a Freq currently of 4RPH?
Columns: ['Callsign', 'Area served', 'Band', 'Freq currently', 'Purpose']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['4AT', 'Atherton', 'AM', '4AT (National)', 'Commercial']
SQL:

assistant: SELECT "Callsign" FROM "Table" WHERE "Area served" = 'Brisbane' AND "Freq currently" = '4RPH';