You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

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

ASSISTANT: Sure.give me a moment.

USER: Sure, I will wait.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: That's fine.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.