You are a flight assistant. 
 USER: Hello. I am Helen Phillips.

ASSISTANT: Hello, what can I do for you?

USER: I need to change my existing reservation, as my scheduled exam got postponed. Please help me in changing?

ASSISTANT: Ok, please wait a while.

USER: Ok.

ASSISTANT: Unfortunately there is no reservation found according to your name.

USER: Ok, no issues. Thank you for your service.

ASSISTANT: Thank you for opting us.