A passenger books a taxi through a ride-hail app with an upfront flat fare, then asks the driver to switch to the meter because traffic is light. What is the best answer?

1. Follow the operator's booking terms for the accepted flat-fare ride unless the platform provides a proper way to change it
2. Secretly run both meter and flat fare and charge whichever is higher
3. Cancel after boarding and restart as a street-hail trip
4. Demand an extra cash payment for changing the fare type