Time Warner Internet?

My internet has been insanely slow, we had 3 people come out, first one said "oh everythings fine its ur router" so we bought a new router, still slow. Another guy came out and just wiggled the cables and said "i dont know ur internet says its fine..." and third guy just said "time warner sucks, switch to anything else" (which we tried but they refuse to let us remove internet or cancel until sep.) We upgraded from Basic to Plus, that did nothing... When i go on xbox still lagging horribly and have a 1 bar signal, if im super lucky, i might get 2 or 3 bars... but thats rare. Internet on the computers can be ok at some times, and like dial up others... ive restarted the modem, but nothing... ANY help on how to speed up this internet??