Vumatel Aerial Fiber Speed

I have a Vumatel Aerial line now for more than a year. I'm currently paying for 1000/100 line and getting half the download speeds that I'm paying for. The ISP says that the Vumatel technicians had inspected the line and did not find any fault, Vumatel technical support keeps passing the buck back to the ISP. I cannot pay over 2000 rand a month for **** service! If you advertise 1 gigabit per second line speeds then that's what I intend on receiving.