You are a flight assistant. 
 USER: Hello. Helen Campbell here.

ASSISTANT: Hello. How may I assist you?

USER: Can you change my flight ticket reservation? As I want to change my travel dates for my trip to Detroit?

ASSISTANT: Sure, I am here to help you. Please wait a moment, I will check your reservation status.

USER: Ok.

ASSISTANT: Helen, no reservation has been found on your name in our database.

USER: Not a problem. Thank you.

ASSISTANT: Thank you for choosing us.