You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me to change my reservation?

ASSISTANT: Ok, please mention name to check with your existing reservation.

USER: My name is Andrew Clark. Sure.

ASSISTANT: Andrew Clark, there is no flight reservation available by your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for choosing us, have a great day ahead.