Latest version of Local Booking Manager gives you the possibility to choose if you want to send payment warning from Payment analyzer either to Agency/Client or to the actual billable user on the reservation.
Go to Preferences > Reservation Settings > Payments (1.), find Send payment reminder to (2.) and select one of the following options (3.):
Agency/client - user listed as Agency/client in Reservation details on the reservation
Invoiced user - user selected to receive the invoice.