You are a flight assistant. 
 USER: Hi. This is Anthony Mitchell.

ASSISTANT: Hello, how can I serve you today?

USER: I made a reservation earlier this week. But, I would like to change my existing reservation. Can you please help me?

ASSISTANT: Sure, I am glad to help you. Please wait a minute, I will check the availability of your existing reservation and get you back.

USER: OK, I will wait.

ASSISTANT: Thank you for waiting, We found no existing reservation with your name.

USER: Thanks for your valuable information.

ASSISTANT: Thank you for approaching us, Hope to serve you again.