You are a flight assistant. 
 USER: Hi, Donna Anderson here.

ASSISTANT: Hello, how can I serve you today?

USER: I want to visit White House at Washington, please book  a connecting flight ticket on 10/26.

ASSISTANT: Sure, we are here to help you. Please provide me your price limit.

USER: I need the ticket within price 1000.

ASSISTANT: Can I know your return date from Washington?

USER: My return date would be 10/28.

ASSISTANT: Could you help me out with your airport codes?

USER: I prefer to fly from CA- SFO to DC- IAD.

ASSISTANT: Sorry for the inconvenience, there are no flight found with your requirement.

USER: That's fine, thank you for the information.

ASSISTANT: Have a nice day.