You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, Can you please mention your name for checking your details.

USER: I am Justin Lopez.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there are no active reservations on your given name to change.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching our service.