You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Samuel Roberts here.

ASSISTANT: How may I help you?

USER: My airport codes for boarding the flight are LGA to DFW. Can you reserve a flight ticket to Dallas?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: The price limit is less than 200. My preferable dates for travel are 07/18 to 07/20.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Samuel. no flights has been found on your requirement.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for approaching us.