You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I'm Timothy Parker. Due to sudden change in my schedule, I want your help in changing my existing reservation. can you please help me?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name to change.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Most welcome.