You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jonathan Mitchell.

ASSISTANT: Mitchell, how may I help you?

USER: I am planning to change an existing  reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure, please give me a moment to check your ticket status.

USER: Sure, take your own time.

ASSISTANT: Sorry Jonathan, no reservation is available by your name.

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

ASSISTANT: Thank you for contacting us.