You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I render you?

USER: I want to change my existing reservation. Can you help me in this?

ASSISTANT: Sure, we are glad to help you.

USER: Thank you.

ASSISTANT: May I know your name, please?

USER: I am Sarah Hall.

ASSISTANT: Sorry, no reservation found on your name in our database.

USER: It's ok. Thank you for your information.

ASSISTANT: Thank you for reaching us.