You pick up call from an otherwise unknown number, the voice on the line asks 'can you hear me?' and when you answer 'yes' they start recording.

They can use that 'yes' to authorize future charges by splicing the audio onto other questions and sign them up for services that can show up on their phone bill or credit cards. For example the "Yes"  can be fraudulently used to switch your utility supplier  without your permission

The Federal Communications Commission has alered consumers about this scam which records their voice and signs them up for...