You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: My name is Thomas Perez. Would you mind helping me in changing my existing reservation details?

ASSISTANT: Sure, I will help you. Please wait for a while.

USER: Ok, I will wait for your response.

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

USER: It's ok, not an issue.

ASSISTANT: Thank you for approaching us.

USER: Thank you for your service.