Really bad internet service

Used to have RAIN's 19 hours Unlimited off-peak for R250pm data plan but after sometime experienced really bad internet speeds, the upgraded to Unlimited 24/7 for R479pm data plan which I thought might have improved speeds, though that was done with much regret! I tried to contact them numerous times. The told me to optimise my device with their tower/signal station which is 0.33km from my house (this should give me amicable speeds). Still that didn't work. I experience less than 1mbps download speed on a constant basis, which is just appalling. My query was then escalated to the network devision. I am yet to hear from them, it's been 3 weeks today.