The "Easiest" way of doing this is via Proxy, however running through a proxy will make your internet suck ass, if they even allow the traffic to pass. (Some limit the type of traffic).
Most Broadband providers give a static IP, HOWEVER, You can TRY to goto
What Is My IP Address - Shows Your IP Address and turn off your router...wait 10sec..plug it back in..and see if it changes... BUT, it'll still be a similar IP, which if traced will come back to the same company.
If you're that worried about it, you can send them a big "I'm sorry, my son was playing, and downloaded a program.."....act Naive... Then say "It'll never happen again.."... if you get someone somewhat sympathetic, they'll turn it back on.
Dont call up cursing them out, and being a complete tool. Don't pull the whole "LET ME SPEAK TO YOUR MANAGER"...
If they say "We don't have that ability" you can reply in a calm voice and say "Do you think your boss could? Can I possibly talk to him?"
Talk to these people like their your friend... not someone who just killed your dog.