You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I help you?

USER: I am Barbara Collins. I want to change my existing reservation,will you help me?

ASSISTANT: Sure, please wait foe while.

USER: Sure.

ASSISTANT: Sorry there is no reservation on your name.

USER: OK,not an issue. Thank you for giving your valuable time.

ASSISTANT: Thanks for availing us.