You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I want to do some changes in my existing reservation, because my friend is unable to attend the tour.

ASSISTANT: How can I assist you? Please mention your name.

USER: My name is Brenda Harris.

ASSISTANT: Sorry Brenda, no reservation found by your name.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for providing valuable information.