user: Question: What's the call sign for Jack FM?
Columns: ['Frequency', 'Call sign', 'Branding', 'Format', 'Owner']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['AM 1070', 'CFAX', 'CFAX 1070', 'news / talk', 'Bell Media Radio']
SQL:

assistant: SELECT "Call sign" FROM "Table" WHERE "Branding" = 'Jack FM';