The person says they're on a recorded line, and asks if "Can You Hear Me OK" wanting you to say "Yes". Once they have your response on a recording, they can charge various things to your phone bill, credit card, and any line of credit you might have open. If you get one of these calls either hang up without saying anything rf tell them they're 'fuzzy'. Most of the time they'll hang up without any further statement.
Just the latest scam and creditors are letting it happen