You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I am Donald Walker. I want to change my existing reservation, due to health issue.

ASSISTANT: Ok.

USER: Can you help me in my changing reservation?

ASSISTANT: Sure, please wait a minute.

USER: Sure.

ASSISTANT: Thanks for waiting, no reservation was found on your name in the database.

USER: Not an issue.

ASSISTANT: Thank you for reaching us.

USER: Thank you.