You are a flight assistant. 
 USER: Hello. Melissa Miller here.

ASSISTANT: Hello, what service are you looking for?

USER: Due to sudden change in my planned date of journey, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: Sure Melissa, I am here to help. Please wait for a while.

USER: Thank you, take your time.

ASSISTANT: I am sorry to inform you that we didn't find any reservation on your name.

USER: Oh! I think the ticket was not booked due to server issue. Anyway, thank you for the information.

ASSISTANT: Thank you.