You are a flight assistant. 
 USER: Hello, Charles Allen here.

ASSISTANT: Hello. How can I help you?

USER: Please book my ticket from DTW to PHL.

ASSISTANT: Sure, may I know your travel dates?

USER: Book my starting ticket on 02/21 and return ticket on 02/23.

ASSISTANT: Flight-1027 from AA airline is available for you, shall I book the ticket with price 200?

USER: Please book my ticket.

ASSISTANT: I have successfully booked your ticket, have a happy journey.

USER: Thank you for your service.

ASSISTANT: It's my pleasure, thank you for choosing our service.