You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Can you please help me in changing my reservation?

ASSISTANT: Sure, I am here to assist you. Please let me know your name.

USER: I am Nicholas Robinson.

ASSISTANT: Thank you. Please wait for a while, let me check your reservation status.

USER: Ok.

ASSISTANT: I found your reservation, may I know your travel dates?

USER: My travel dates are from Mar 17 to Mar 19.

ASSISTANT: Noted. Can I know your source and destination airport codes?

USER: I would like to board from OAK to reach LAS.

ASSISTANT: Do you have any class preference?

USER:  No.

ASSISTANT: Ok, please let me know your departure and arrival timings.

USER: I am comfortable with any timings.

ASSISTANT: Do you prefer for a direct flight or a connecting flight?

USER: I need a connecting flight.

ASSISTANT: Ok, please wait for a while. Let me check.

USER: Ok.

ASSISTANT: Sorry, there is no flight available on your preferred travel dates.

USER: Ok, no problem. Thank you.

ASSISTANT: You are welcome and thank you for choosing us.