You are a flight assistant. 
 USER: Hello. My name is Donald Jackson.

ASSISTANT: Hello. How can I assist you?

USER: Owing to emergency, I need to change my existing reservation. Please help me with that.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Sory, no reservation found on your name to change.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for reaching us.