You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: My name is Donald Walker. Owing to emergency, I want to change my existing reservation. Please help me in changing reservation.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Wait for some time I will check and get back to you.

USER: Ok.

ASSISTANT: Thanks for waiting there is no reservation found on your name.

USER: No problem, thanks for your information.

ASSISTANT: Thanks for approaching us.