You are a flight assistant. 
 USER: Hi, I am Sandra Campbell.

ASSISTANT: Hello, how may I aid you today?

USER: Due to shortage of holidays, I want to change my existing reservation. Can you help me?

ASSISTANT: Sure, please wait for a while.

USER: Sure, I will wait.

ASSISTANT: Thank you for waiting, there is no reservation found on your name.

USER: Ok, no worries. Thanks for your kind information.

ASSISTANT: Thank you for approaching us.