When you receive a booking request, you will have 24 hours to accept or decline it. FishingBooker will send you a text message and an email every 8 hours to remind you about the booking request if you haven't accepted or declined the trip in the meantime.
You must accept or decline the booking request through your Manage Bookings page. Sending an Instant Message to your customer does not equate to accepting or declining a booking.
If you don't respond within 24 hours, the request will be automatically declined and your listing will receive a rankings drop.