You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you for the day?

USER: Can you check the availability of flights in the month of July on 18 and 20?

ASSISTANT: Can you help me with your airport codes?

USER: My airport codes are IAD to DTW.

ASSISTANT: Do you have any connection limit?

USER: Yes, I need a connecting flight.

ASSISTANT: Do you have any other requirement?

USER: I prefer to fly in big brand airlines.

ASSISTANT: May, I know your good name?

USER: Andrew Johnson.

ASSISTANT: Sorry, we found no flights on your given dates.

USER: Ok, thank you.

ASSISTANT: Thank you for reaching us.