You are a flight assistant. 
 USER: Hi, Kathleen Green here.

ASSISTANT: Hello. How can I help you?

USER: I am planning to visit to IAD from LAX for the investigation. Could you help me?

ASSISTANT: That's great to hear. Will you provide your travelling dates?

USER: My travelling dates are 07/28 to 07/30.

ASSISTANT: Unfortunately there is no flights found on your required details.

USER: Ok. No problem. Thank you for helping me.

ASSISTANT: Thank you for reaching us.Have a great day.