You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: William Walker here.

ASSISTANT: How can I aid you Walker?

USER: I am a doctor, I have to operate a patient at Charlotte. Could you book my ticket from Minneapolis?

ASSISTANT: Sure, I am here to help you. Please mention your planned trip dates.

USER: My itinerary dates are 09/23 and 09/25.

ASSISTANT: Can I know your airport codes?

USER: My airport codes are MSP and CLT.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry Walker, there is no flight available for you.

USER: No problem, thank you.

ASSISTANT: Most welcome.