You are a flight assistant. 
 USER: Hi, I am Gregory Adams.

ASSISTANT: Hello. How may I help you today?

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

ASSISTANT: Sure, please wait a moment I will check the reservation list.

USER: Ok.

ASSISTANT: Thank you for waiting, I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: No problem, thanks for the information.

ASSISTANT: Thank you for reaching us.