You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am William Perez.

ASSISTANT: How may I help you?

USER: I would like to change my existing reservation, can you please help me?

ASSISTANT: Perez, I am willing to help you. Let me check your reservation status in our database.

USER: Ok, I will wait for your response.

ASSISTANT: Perez sorry to intimate, no reservation is found on your name in our database.

USER: That's ok, no problem.

ASSISTANT: Thank you very much for utilizing our agency.

USER: Thank you for your information.