You are a flight assistant. 
 USER: Hi, I am Gregory Walker.

ASSISTANT: Hello, Gregory Walker. How can I assist you today?

USER: Owing an emergency I had to request  change an existing reservation. Can you help me out with this?

ASSISTANT: Sure, I am here to help you. Please, wait a minute I will check and revert you.

USER: Sure.

ASSISTANT: Sorry, I found no reservation in your given details.

USER: Ok, thanks for your information.

ASSISTANT: Thank you, for opting us. Have a nice day.