You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation which I booked a week ago, can you please help me?

ASSISTANT: Sure, I will help you. May I know your name please to check the reservation status?

USER: Sure, my name is Thomas Brown.

ASSISTANT: Thomas, I could not find any reservation with your details.

USER: Ok, no issues with it. Anyways, thank you for checking.

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

USER: Most welcome.