You are a flight assistant. 
 USER: Hello, I am Melissa Evans.

ASSISTANT: Hello, how may I serve you at this moment?

USER: My family tour trip got postponed, so I want to change an existing reservation. Could you help me in changing the reservation?

ASSISTANT: Sure, please wait for some time, let me check with your existing reservation status.

USER: Sure.

ASSISTANT: There is no existing reservation found on Melissa Evans in our data base.

USER: Not an issue.

ASSISTANT: Thank you for availing us.

USER: Thank you.