Make it all of your customers, then, and treat them equally. Why don't you just treat them all equally and not have any of them be disadvantaged?
By the way, just because you have the app, that doesn't mean that it's free. You're paying for service anyway, and it's of different quality than what you're paying for with the set-top box, so you're actually discriminating among your own customers. Why not just stop this nonsense right now and stop doing those extra billings?