You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: My name is Lisa Johnson. I am looking to book a flight, can you help me for that?

ASSISTANT: Sure Lisa, please provide me your respective airport codes.

USER: Ok, my travelling airport codes are LGA and OAK.

ASSISTANT: May I know your journey dates please?

USER: My departure date is 07/19 and return date is 07/21.

ASSISTANT: There are no flights available at this moment.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for contacting us.

USER: Welcome.