You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Donna KIng.

ASSISTANT: How may I serve you?

USER: I want to change my existing reservation as my trip got rescheduled, please help me out.

ASSISTANT: Sure, please stand by.

USER: Ok.

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

USER: No issues, thank you.

ASSISTANT: Thank you for reaching us.