You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Nancy Smith here.

ASSISTANT: How may I guide you today?

USER: My preferable dates for travel are 04/19 to 04/21. Can you reserve a flight ticket? The price limit is less than 1000.

ASSISTANT: Sure, I will help you with that. Can you please share your source and destination airport codes?

USER: My airport codes for boarding the flight are IAH to HOU.

ASSISTANT: Please wait for a minute.

USER: Ok.

ASSISTANT: I am sorry to say that there is no flight found under your details.

USER: No problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.