You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Patrick Johnson here. I want to change my existing reservation to new dates.

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name ton change.

USER: It's ok, thanks for your assistance.

ASSISTANT: Welcome. Thank you for choosing us.