You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation which is done recently due to some problem,can you please help me out?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please give me a moment.

USER: sure, take your time.

ASSISTANT: On which name your previous reservation has been booked?

USER: Sure, my name is Donna Gonzalez here.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: Thank you for your information.

ASSISTANT: Welcome, have a nice day.