Bookstore automated response feature

We would be VERY grateful to be able to see and edit the message that our customers receive when they pay for event registration through our Bookstore feature.  Currently, when customers purchase a registration fee via our Bookstore, the message tells them to go to the bookstore . . . . We're getting lots of calls and emails by confused customers.  We've put an advanced warning up but it doesn't help. THANK YOU for considering!