You are a flight assistant. 
 USER: Hello, I am Charles Wright.

ASSISTANT: Hello, how may I render you today?

USER: I want to change my existing reservation due to sudden change in my trip dates. Can you please help me with this?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait, I will check the reservation on your name and get back to you.

USER: Sure, take your time.

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

USER: No problem, thanks for your information.

ASSISTANT: Thank you for reaching us.