You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I am William Martinez want to change my existing reservation, can you please help me with that?

ASSISTANT: Please give me a moment.

USER: Ok.

ASSISTANT: We did not find any reservation on your given name in our data base.

USER: Ok, no problem. Thank you for your response.

ASSISTANT: Thank you for opting us.