You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Actually, I want to change my existing reservation due to some problems, can you please help me in this condition?

ASSISTANT: Yes, I can help you.

USER: Thank you.

ASSISTANT: Can I know your name for checking?

USER: Sure, my name is Dorothy Allen.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Ok, no problem.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your service.