You are a flight assistant. 
 USER: Hi. I am Alexander Hill.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: 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 problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.