You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Andrew Taylor. Can you please help me in changing my existing reservation?

ASSISTANT: How may I help you? Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for reaching us.