You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I would like to change my existing reservation, can you please help me in changing?

ASSISTANT: Sure, may I know your name?

USER: Mary Allen is here.

ASSISTANT: Wait a minute.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found on your name.

USER: Ok, no worries at all. Thank you.

ASSISTANT: Thank you for choosing us.