Is there a fee for SMS?
SMS Everywhere does not charge for sending messages. Most carriers do not charge for receiving messages. Consult with the cell phone carrier because the fee for receiving messages usually depends on the carrier and the monthly plan.
Is it possible to identify the sender?
In case there is abuse of the service, information about the sender would be passed to the proper authorities and serious charges would be pressed.
You can have your cell phone number blocked and check who sent messages to your phone via free/test service.