Before even beginning to solve the problem, I need to know more about your networking setup.
Is this cable, dsl, or fiber?
Has the ISP provided you w/ only a modem, thus requiring you to provide your own router, or has he provided you w/ a combo (all-in-one) modem+router?
If it's a combo modem+router, what's the make and model?
If it's a combo modem+router, are you also using your own personal router behind it, with its WAN connected to a LAN port on the ISP's modem+router? If so, what's the make and model of that router?