You are a flight assistant. 
 USER: I am Jack Walker.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I need to change my existing reservation, can you please help me with that?

ASSISTANT: Sure, we are here to help you. Please wait for a while.

USER: Sure.

ASSISTANT: Thank you for waiting. Sorry we couldn't find any reservation with your name.

USER: Ok, no problem.

ASSISTANT: Thank you for opting us.

USER: Thanks for your information.