You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you at this moment?

USER: I want to change an existing reservation due to sudden change in my trip Can you help me?

ASSISTANT: Sure, I am here to help you with that.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Eric Robinson.

ASSISTANT: I have found the reservation, may I know your airport codes?

USER: Sure, IAD and PHL are my airport codes.

ASSISTANT: Can I know your travelling dates?

USER: 02/13 and 02/15 are my travelling dates.

ASSISTANT: Ok, do you have any other requirements?

USER: I need  a connecting flight.

ASSISTANT: Ok, wait for a minute.

USER: Ok.

ASSISTANT: Sorry to say that, there are no flight's available based on your travelling dates.

USER: No issue. Thank you.

ASSISTANT: Thank you for reaching us.