You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Patrick Garcia from Oakland.

ASSISTANT: What service that you are seeking from our agency Garcia?

USER: I want to change my travel dates in my previous reservation, due to some problems I am unable to travel those dates so can you please help me with that?

ASSISTANT: Sure, I am glad to help you.

USER: Thank you.

ASSISTANT: Please wait a moment to check your previous reservation.

USER: Ok.

ASSISTANT: We regret that, there is no reservation with your name in our records.

USER: Oh! May be I am not booked my ticket properly at that time.

ASSISTANT: Thank you for approaching us, hope you have a great day.

USER: Thank you for your service.

ASSISTANT: Welcome.