You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I am Justin Perez. I want to some change an existing reservation because my friend's are not are not able to come on that dates.Can you please help me with that?

ASSISTANT: Sure, I will help you. Please wait a moment, I will check is there any previous reservation available or not on your name.

USER: Sure, take your own time.

ASSISTANT: No previous reservation found on your name Justin Perez.

USER: That's fine. Thank you for your service.

ASSISTANT: Thank you for contacting us, have a nice day.