LNP and exclusivity agreements

One of the technical problems I've been wrapping my brain around for the past few days has been integrating local number portability customers for various local telecomm carriers, as we're expanding support for our SMS-based breaking news service. The conundrum is that while we offer the service exclusively to select carriers, and filter our ineligible customers by validating their phone number(s) at registration by evaluating their prefixes, customers coming from external carriers get locked out.

Were we to open this up, we'd lose the exclusivity advantage, with the service being available to anyone. If we keep it closed, it makes the platform less valuable to potential wireless clients, and for us, that's one more person who could be reading my stuff.

Also, I've been looking into the matter and have noted that LNP services may only apply to voice, not data and/or SMS packets. Ouch.