I generally preempt at the end of the call by saying, "Thanks, Ms. Green, for meeting all of my travel needs, today."
It is a requirement to ask for the Hertz rental and if all your travel needs were met and if not asked and call is monitored, points will be lost and if the total score does not meet the standard it will eventually lead to disciplinary action. If the caller ends with "No I don't need a car and you met my travel needs or answered all of my travel questions" all the call closing requirements are satisfied. It stinks when time is of the essence for the caller and the closing just seems to burden the caller, you gotta do what you have to do.