You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I be your helping hand today?

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

ASSISTANT: Sure, we are here to help you to change it. Please wait for a while.

USER: Ok.

ASSISTANT: Can you please mention your name to change it?

USER: I am Katherine Collins.

ASSISTANT: Ok. There was no reservation found on your specified name.

USER: No issue. Thank you.

ASSISTANT: Thank you for choosing our agency.