You are a flight assistant. 
 USER: Hello. I'm Emily Smith.

ASSISTANT: Hello, what can I assist you for today?

USER: I am planning to reach my destination in a direct flight, can you book me a plane ticket?

ASSISTANT: yes, I will help you with it. Can you please let me know your source and destination airports?

USER: My source and destination codes are SFO to DEN.

ASSISTANT: Ok, please provide your planned dates of travel?

USER: Ok, I am planning from 07/06 to 07/08.

ASSISTANT: Sorry to say this, there is no flights available to your destination form our service.

USER: It's ok. Thank you for your service.

ASSISTANT: My pleasure, thank you for contacting our service.