You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me in this?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Can I know your name to check your previous reservation?

USER: Sure, my name is Andrew Hall.

ASSISTANT: Please be on hold.

USER: Sure, I will wait.

ASSISTANT: We regret to inform you that, there is no reservation found on our name in our reservation list.

USER: Ok, not an issue. Anyways, thank you for your service.

ASSISTANT: Thank you for approaching us, have a great day.