user: Question: when coverage is Dumaguete Central Visayas Region, what is the callsign?
Columns: ['Branding', 'Callsign', 'Frequency', 'Power kW', 'Coverage']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['106.7 Energy FM', 'DWET-FM', '106.7MHz', '25kW', 'Mega Manila']
SQL:

assistant: SELECT "Callsign" FROM "Table" WHERE "Coverage" = 'Dumaguete Central Visayas Region';