You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I give some help at this time?

USER: Unfortunately, I would like to change my existing reservation due to some problems, can you please help me in this intent?

ASSISTANT: Yes, I can help you in that one. May I know your name for checking purpose?

USER: Sure, my name is Sandra Carter.

ASSISTANT: Please give me a moment to check it.

USER: Sure, take your time.

ASSISTANT: As per your request there is no reservation found on your name to change it.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Thank you for your appreciable service.

ASSISTANT: Welcome.