You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Ruth Thompson. I want to visit my sister, could you help me in booking the ticket?

ASSISTANT: Sure, can I know your travelling dates?

USER: It's from JFK to DFW. The dates of travel are from 08/20 to 08/22.

ASSISTANT: Ok, give me a moment. Sorry to say that there are no flights found matching your requirement.

USER: That's ok. Thank you for your time.

ASSISTANT: You are welcome.