Poor service & fibre line

I got a 10mg fibre line, which should have a constant speed of atleast 9mg in the slowest times. But yet I barely get a 1mg speed. Ive compained on their whatsapp service had feeback twice out of the 4 complaints. And all of them say they are investigating and yet nothing happens. I should pay R550 a month yet they billed me R640 and when I rep**** to the invoice and asked why, I didnt get feedback either. So I either I get my 10mg speed as a constant. Or I move.