You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, on which name can I change your reservation?

USER: It was reserved in the name of Ronald Martinez.

ASSISTANT: I am sorry no reservation found on your name.

USER: Ok, fine. Not  an issue. Thank you for your help.

ASSISTANT: Thank you for choosing us.