You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donald Jackson.

ASSISTANT: How can I help you at this moment?

USER: I want to change my existing reservation. Can you please help me with this?

ASSISTANT: Sure, I will help you in changing your reservation. Please give me a moment to check your reservation status.

USER: Sure.

ASSISTANT: Donald Jackson, there is no active reservation found under your name in our database.

USER: Ok, not an issue. Thank you for the information.

ASSISTANT: Thank you for utilising our service.