You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you for today?

USER: I am Robert Mitchell here, I want to book a ticket from OAK to AUS, can you please help me to book a ticket?

ASSISTANT: Ok, can you please mention your travelling dates for the following journey?

USER: Sure, my dates of journey is from 04/27 to 04/29. Please make sure that the price limit is 200.

ASSISTANT: Sorry, no flights are available on your requested route.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.

ASSISTANT: Most welcome.