You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Anna Phillips.

ASSISTANT: Anna, how may I help you?

USER: I want to visit my sister's home for her birthday, can you help me?

ASSISTANT: Sure, provide me your airport codes?

USER: It's IAD to SEA.

ASSISTANT: Can I know your travelling dates?

USER: The dates of travel are 09/28 to 09/30.

ASSISTANT: I am sorry for our inconvenience, there is no flight available with your provided details.

USER: That's ok. Thank you for your time.

ASSISTANT: My pleasure.