user: Question: What is the call sign of the Classic Country Music station?
Columns: ['Frequency', 'Call sign', 'Name', 'Format', 'Owner']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['88.7 FM', 'KFBN', 'Heaven 88.7', 'Christian', 'Fargo Baptist Church']
SQL:

assistant: SELECT "Call sign" FROM "Table" WHERE "Format" = 'Classic Country';