Changing number of guests on a booking does not prompt the credit card screen for payment

I believe this is a defect in current functionality but was told I had to submit a function request.  When a user creates a reservation with 1 guest, then edits it to add more guests, or changes reservation types from Singles with Guest to Doubles with Guest (allowing up to 3 guests), the system does not bring up the credit card screen to allow the user to pay for the additional guests.  It merely adds the charge to the account but the user does not realize he owes more money and never pays.  Our staff then have to chase for payment.  Please fix this so that when more money is owed, the user is prompted to pay before completing the edit.