You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Donald Perez here.

ASSISTANT: How may I help you out?

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, I will help you in changing the ticket.

USER: Thank you.

ASSISTANT: Sorry, there are no reservations found.

USER: Oh! Not an issue.

ASSISTANT: Thank you for reaching us.

USER: Anyway, thank you for the information.