You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Gregory Lee.

ASSISTANT: How can I serve you today?

USER: I would like to change my existing reservation.Could you please help me with reservation?

ASSISTANT: Sure, please wait for some time, let me check with your existing reservation status.

USER: Sure.

ASSISTANT: There is no existing reservation find on your name.

USER: Ok, no issues.

ASSISTANT: Thank you for approaching us.

USER: Thank you for your information.