You can make prices changes for each of your Services from the Petcare > Services & Times > Base Services page by editing each services. When you save use the Effective Date to apply the new prices to existing visits in the system. NOTE: the Effective Date is a one-time setting and only affects visits already in the system that moment (new visits added/requested will always use the new pricing regardless of date) so only make the price changes once you no longer expect new requests for before the Effective Date

If you made price changes without using the Effective Date you can also updates prices for existing visits by bulk selecting them on the Master Schedule and doing a Recalculate.