A friend of mine discovered a weird loophole at some Danish ISPs. Most of the ISPs doesn't allow you to use your own router, but they can open up your "port" to accept any router. Calling in, saying that you have a Cisco router than you can't get working, just playing dumb about the being locked to the ISP provided router, they'll then assume that you know what you're doing because "Cisco" and unlock your account.