You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself David Davis.

ASSISTANT: How can I assist you?

USER: I want to change my existing reservation, can you help me in that?

ASSISTANT: Sure, we are happy to help you.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Sure, I will wait for your response.

ASSISTANT: Thanks for waiting, there is no active reservation on your name in our data.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for opting us.