4 Months No internet and they dont give a ****

Worst service in the world. I have not got more that 0.4mb/s down and 0.2mb/s up on my 4mb/s line since they installed it. i am refusing to pay until they sort it out. over 30 complaints and 20 callouts and its still not working. They close the complaints saying service restored when they have done nothing. I have complained to managers, managers of managers and they have all done the same, promise me that someone will come sort out mu problem. But they never do. Still 4 MONTHS!!!! with out functional Internet. They have found power on the line by checking the noise on the line and have not had anyone come out and check the power/noise problem.