You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joshua Williams.

ASSISTANT: How can I assist you today?

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

ASSISTANT: Ok, I will assist you with your concern.

USER: Thank you.

ASSISTANT: Please wait a moment while I check.

USER: Sure.

ASSISTANT: Ok, thank you for waiting. Sorry, there is no reservation been found on your name to proceed.

USER: That'd fine, thank you for service.

ASSISTANT: Thank you for choosing our agency.