You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: Can you please help me to modify my existing reservation?

ASSISTANT: Sure, will you mention your name for checking the reservation status?

USER: Yes, I am Christopher Miller.

ASSISTANT: Please give me a moment.

USER: Sure, I will wait for your reply.

ASSISTANT: There is no reservation found under your name.

USER: That's ok, thank you for your service.

ASSISTANT: Welcome, have a great day.