You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: Sure, please wait a moment.

USER: Ok.

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

USER: No issue. Thank you.

ASSISTANT: Thank you for approaching us.