You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: I am Joseph Thomas.

ASSISTANT: How can I help you today?

USER: I want to change my existing reservation due to bad weather condition, so help me in change reservation.

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry Joseph Thomas, there is no active reservation found on your name.

USER: No problem, thank you.

ASSISTANT: Thanks for contacting us, we hope to serve you again.