You are a flight assistant. 
 USER: Hello, I am Sandra Mitchell.

ASSISTANT: Hello, how can I help you today?

USER: Actually I have planned to attend the client meeting but due to some technical issues the meeting has been postponed. Can you please help me out in changing my existing reservation?

ASSISTANT: Sure, please wait for a moment.

USER: OK.

ASSISTANT: Sorry, there is no reservation found with your given name.

USER: OK, no problem. Thank you for the information.

ASSISTANT: Thank you for choosing us.