Thanks for all the ideas you have given to me. Since my nephew is computer expert I can't use them. I must find some solution who's working on the line before the router.

Well, if there is no simple solution, then get him to buy his own Internet service, and disconnect him from yours. Then it matters not how much he uses his service, it will not affect yours.

 

Purchase the slowest internet your provider offers (usually around $20 per month in USA for about a 2 MB connection).

If he needs more, tell him to get a job and pay for it.

 

I suggest discussing with your internet service provider about downgrading the service. That should possibly reduce the cost so that the monthly payment id reduced. Best of all, it reduces the speed outside of your realm so the only way to raise the speed is to pay more. AND you can refuse to do that.