You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I need to change my existing reservation.

ASSISTANT: How can I serve you? Sure, please provide me your name.

USER: My name is Alexander Clark.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, unfortunately there is no reservation found with this name.

USER: No issue. Thanks for the information.

ASSISTANT: Thanks for picking us.