You are a flight assistant. 
 USER: Hi. Rebecca Brown here.

ASSISTANT: Hello, how may I guide you at this moment?

USER: Due to health issues, I need to change my existing reservation. Please help me in changing recent reservation.

ASSISTANT: Sure, we are here to help you in that.

USER: Thank you.

ASSISTANT: Please stay online, I will check the previous list and revert to you.

USER: Sure.

ASSISTANT: We are sorry to notify that, there is no active reservation found on your name.

USER: Thanks for your information.

ASSISTANT: Thanks for communicating with us.