user: Question: What is the call sign of the station with the frequency of 90.3MHz
Columns: ['Branding', 'Callsign', 'Frequency', 'Power (kW)', 'Location']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ["Mom's Radio 97.9 Laoag", 'DWSN-FM', '97.9MHz', '5kW', 'Laoag']
SQL:

assistant: SELECT "Callsign" FROM "Table" WHERE "Frequency" = '90.3MHz';