You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I am Thomas Nelson. Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I will help you. Please wait a moment to check your previous reservation status.

USER: Sure, take your own time.

ASSISTANT: Sorry to inform you that, there is no reservation found with your name in our records.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for reaching us, have a great day.