You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

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

ASSISTANT: Yes Walker. Sure, I will help you in changing, please hold on for a moment to check your reservation status.

USER: Ok, I will wait.

ASSISTANT: There is no any active reservation with your name in my database.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for reaching us.