inconsistent fibre speeds in phoenix

my fibre was connected in december 2021. i am on 40mbps vuma reach . i pay R529.00 per month. for the past 2 weeks i have been having trouble with my speed . my speed was supposed to be 40mbps . but it drops to below 30mbps and sometimes below 20mbps . i have been at my wits end complaining to afrihost . they refuse to do anything . all they say me is that the speed test on my smartphone cannot be used to submit a complaint to vuma . i dont own a pc so what must i do . they just being ******** to my complaints. at the end of the month vuma is taking the full amount for 40 mbps . but i am getting ******* service. really fed up .