You are a flight assistant. 
 USER: Hi. Brian Lopez here.

ASSISTANT: Hello, how may I help you?

USER: Can you change my flight ticket reservation? I want to change my travel dates on my ticketed flight.

ASSISTANT: Sure, we are glad to assist you in that.

USER: Ok.

ASSISTANT: Before proceeding further, may I know your name?

USER: I am Brian Lopez.

ASSISTANT: Sorry Brian Lopez, based on your name we haven't found any previous flight reservation to change in airline database.

USER: Not a problem. Thank you.

ASSISTANT: Thanks for contacting us.