You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I am David Smith from Washington. I want to change my travel dates in my previous reservation so can you please help me with that?

ASSISTANT: Sure, I am here to help you to make a change of reservation, please wait for a minute.

USER: Ok, thank you.

ASSISTANT: Sorry, I could not find any reservation with your name in our database.

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: Thanks for choosing us.