What is the true purpose behind the service address (SA) vs the billing address(BA)
I assume the request for billing address is to communicate paper mails where digital communication is not possible due to either geographic or physical constraints.
The service address would be know the most used location/geographically fenced location for offering a service as those services cannot be offered reliably beyond the confines of a fenced location like emergency services or signal quality services.
Third party hardware authenticators with gps or non gps geolocation/timing could enforce such a logic to support the service.
Take the case of a homeless traveller with a PO Box and without a place to call home will not be able to avail the use free/open services like Skype.