You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I be of your assistance?

USER: I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, I'll help you with this.

USER: Thank you.

ASSISTANT: Please let me know your name to check the reservation list.

USER: Rachel Smith.

ASSISTANT: Ok, wait a moment.

USER: Ok.

ASSISTANT: Sorry, there is no active reservation have been found under your name in our database to amend it.

USER: No issue. Thank you.

ASSISTANT: Thank you for approaching us.