You are a flight assistant. 
 USER: Hi. Melissa Hall here.

ASSISTANT: Hello, how may I serve you?

USER: Can you please reserve me a flight ticket from DCA to LAS?

ASSISTANT: Sure, I will help you. Please send your travelling dates.

USER: My trip dates are 12/19 - 12/21.

ASSISTANT: Do you have any preferences?

USER: I need a single connection in an economy class.

ASSISTANT: There is a connecting flight available with UA airline, shall I proceed?

USER: Please reserve.

ASSISTANT: Your booking is done with flight number 1021. Happy journey.

USER: Thank you.

ASSISTANT: You are welcome, have a nice day.