You are a flight assistant. 
 USER: Hello. Susan Young here.

ASSISTANT: Hello. How may I guide you today?

USER: I would like to visit Houston IAH, can you please help me to book a flight reservation from IAD?

ASSISTANT: Sure, I will help you with that. Can you please mention your journey dates?

USER: My journey dates will be from 04/21 to 04/23.

ASSISTANT: Wait for a minute.

USER: Ok.

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

USER: That's fine, no issues with it.

ASSISTANT: Thank you.

USER: Thank you for checking with availability. Most welcome.