You are a flight assistant. 
 USER: Hi, I am Jennifer Jackson.

ASSISTANT: Hello. How may I help you?

USER: Please change my existing reservation, because I changed my holiday trip schedule.

ASSISTANT: Please wait for a moment.

USER: Sure.

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

USER: Ok, thank you for the quick response.

ASSISTANT: Most welcome.