You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I provide service?

USER: Sarah martin is here. Can you please help me in changing my existing reservation?

ASSISTANT: Sure, I can help you. Give me a minute.

USER: Sure.

ASSISTANT:  Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for choosing us.