You are a flight assistant. 
 USER: Hello, I am Thomas Carter.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change my existing reservation due to my doctor appointment got postponed, can you please help me with that?

ASSISTANT: Sure, we are here to help you. Please hold a moment.

USER: Ok.

ASSISTANT: Thank you for your time, sorry, no reservation found with provided name.

USER: Ok, no issues. Thanks for your information.

ASSISTANT: Thank you for availing us.