You are a flight assistant. 
 USER: Hello. Andrew Perez here.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, please wait for a moment.

USER: Ok, take your time.

ASSISTANT: Sorry, there was no reservation found with your given name.

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

ASSISTANT: Thank you for opting us.

USER: Welcome.