I am paying for 18Mbps, when I connect my pc directly to the modem, I get 17.56Mbps, after rebooting the router, I get about 10Mbps. then it quickly drops to 2-5 Mbps. this has been going forever, I have bought 3 routers of different brands, I have tried factory reset, firmware is update, changing the mtu size, I have tried every channel. I am out of ideas, please help.