When you receive a proposal from the travel agency, you see it in the My Trips tab under Plans, with the status Proposal(s) pending for review.
Click the trip name to display your options. Typically the display begins with a main proposal that the travel agency has provisionally booked.
This is immediately followed by one or more alternate proposals that have not been booked.
Under YOUR SELECTION at the bottom of the screen, choose one of the proposals by clicking its corresponding radio button.
Click Confirm the selection.
The trip now proceeds through the normal approval process. When the trip is approved, the booking is sent for ticketing.
If none of the proposals from the agency suits your requirements, you will need to contact the agency and discuss the situation with them. You cannot change your original travel request yourself, but following your discussion the agency will be able to offer and synchronise new proposals via the travel request.