I've got this contract with my ISP saying lots of uninteresting stuff like I'm not allowed to use my internet connection to this and that, I'm not allowed to do even more of this, and not that, and so on. But until now I haven't found one single word about me not beeing allowed to config "my" (read: the router I got from them, which really still is their property) router to forward ports to different IP's in the local network (nat) at home.

This kinda restricts the use of my network since alot of stuff needs to work in a state where it isn't "behind a firewall", I've tried to ask my ISP for the port forwarding user/pass, but they don't even respond (2 months now), and it has just gotten on my nerves. Anyone have a reasonable solution? All I want is to forward a couple of ports, but they just don't seem to let me.