You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Alexander Anderson. I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure Alexander Anderson, let me check your reservation status in our database.

USER: OK.

ASSISTANT: Sorry to inform you, no reservation is found with your criteria.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you very much for utilising our agency.