To change the date or time of your appointment, open the booking from your Bookings tab and tap Reschedule. You can then pick a new date and time from the provider's available slots. The provider may need to confirm the new time depending on their settings.
If no suitable slots appear, the provider might be fully booked for the period you want. Try another date or message the provider to ask about availability. Once rescheduled, you will receive an updated confirmation and the booking detail will show the new time.