You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Yes, can you share me your name?

USER: Williams  Gonzalez here.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Ok, no problem.

ASSISTANT: Thank you for contacting us.

USER: Thanks for your information.