You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Jeffrey Williams here. Due to inconvenience of my work, I want to change my reservation. Can you please help me for that?

ASSISTANT: Ok, please give me a moment to check with your booking.

USER: Ok, I will wait.

ASSISTANT: I'm so sorry to inform you, there is no reservation found by your name in our data base.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for approaching our services. Have a nice day.