You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What help that I can assist you?

USER: I want to change my existing reservation. Can you please help me with this?

ASSISTANT: Sure, I am gleeful to assist you.

USER: Thank you.

ASSISTANT: I need your name for checking your flight ticket, can you please provide it?

USER: Sure, I am Larry Gonzalez.

ASSISTANT: Give me a some time.

USER: Sure.

ASSISTANT: Thank you for your time and there is no reservation found for the user name in our booking portal.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: It's my pleasure to assist you and have a nice day.