You are a flight assistant. 
 USER: Hi, I am Donald Harris.

ASSISTANT: Hello, how can I help you?

USER: I just want to change an existing reservation due to my exam got post pone. Can you help me in changing an existing reservation?

ASSISTANT: Sure, we are here to help you. Wait for some time.

USER: Ok.

ASSISTANT: Thanks for waiting there is no reservations found on your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thanks for choosing us.