The payments between passengers and driver are handled in cash at the end of the ride. The amount the passenger has to pay is shown to them prior to the ride in the Detail View of their Request or by pressing the+ button in the Riding Tab, after the driver accepted the ride.
However, Wunder does not charge the driver or passenger.
The payment is done in cash between the passenger and the driver. Once you request a ride, you will see the price of the ride. Click on the ride (the + bottom top right), if you auto-requested, and check for the price.