You are a flight assistant. 
 USER: Hi, I am Amanda Phillips.

ASSISTANT: Hello, how can I serve you?

USER: I want to do some changes in the existing reservation because my friends are not able to come on those dates, can you help me in changing an existing reservation?

ASSISTANT: Sure, give me sometime to check and revert to you.

USER: Ok.

ASSISTANT: Thank you for waiting. Unfortunately we didn't found any reservation according to your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for opting us.