You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I support you?

USER: I am Christopher Lewis. I want to change an existing reservation due to sudden change in my trip.

ASSISTANT: Ok.

USER: Can you help me?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while, I will check your reservation.

USER: Ok.

ASSISTANT: Thank you for your time, there is no previous reservation found on your name.

USER: No issue. Thank you.

ASSISTANT: Thank you for contacting us.