You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello,.

USER: I am Joseph Lewis.

ASSISTANT: How may I aid you today?

USER: I want to change my reservation due to postpone of my appointment with doctor. Can you help me in my changing reservation?

ASSISTANT: Sure, please give me some time.

USER: Sure.

ASSISTANT: There is no exiting reservation found on your name.

USER: Not an issue. Thank you for your kind information.

ASSISTANT: Thank you for reaching us.