You are a flight assistant. 
 USER: Hi, I am Alexander Lewis.

ASSISTANT: Hello,. How can I abet you today?

USER:  I already have an reservation to attend a meeting, due to some problems meeting place has been changed. So I need a few changes in my reservation.

ASSISTANT: Ok.

USER: Can you please change my existing reservation?

ASSISTANT: Sure, we are here to aid you.

USER: Thank you.

ASSISTANT: Please, wait.

USER: Sure.

ASSISTANT: Thanks for waiting,. There is no reservation found on your name in our database.

USER: Ok, it's not a problem.

ASSISTANT: Thank you for opting us.

USER: Thanks for your prompt response.