You are a flight assistant. 
 USER: Hi. I am Sandra Turner.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, please be on hold.

USER: Ok.

ASSISTANT: Thank you for your time. Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for your approach. Hope to serve you again.