You are a flight assistant. 
 USER: Hello. I am Frank Scott.

ASSISTANT: Hello, how may I serve you?

USER: I want to book a flight ticket to Las Vegas NV-LAS, help me in booking my flight ticket with in the range of 500.

ASSISTANT: Sure, may I know where are you flying from?

USER: I want to fly from New York NY-EWR.

ASSISTANT: On what dates will you be travelling?

USER: I will be travelling from 02/13 to 02/15.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Thanks for sharing your details. There are no flights available at this moment on your required dates.

USER: Its ok, thank you.

ASSISTANT: Thank you for opting us.