To change the price of a Service within a Reservation, locate the Reservation on the Bookings screen and tap on it

If the Reservation only has one Service in it, or if you'd like to change the Price of the overall Reservation, it can be changed in the Price field

Tap directly on the price, enter a new price and tap SAVE

If the Reservation has multiple Services, you can change the price of an individual service by scrolling to the Services section and long tapping on the relevant Service and selecting Edit

Edit the Price and tap SAVE