You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Ashley Lewis, want to alter my recent reservation. Please help me out with that.

ASSISTANT: I have found your reservation. May I know your travelling dates?

USER: My travelling dates are from 01/28 to 01/30.

ASSISTANT: May I know your airport codes?

USER: My airport codes are from IAD to PHL.

ASSISTANT: There is no flights available on these dates.

USER: It's ok, thank you.

ASSISTANT: Welcome.