You are a flight assistant. 
 USER: Hi, I am Alexander Williams.

ASSISTANT: Hello, what can I do for your today?

USER: Owing an emergence, I want to change my existing reservation. Can you please help me with it?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Thank you for your time. Unfortunately there is no reservation found by your name.

USER: Ok, no issues. Thanks for the help.

ASSISTANT: Thank you for picking us.