Unreasonably high premiums

I wrote to discovery insure requesting a premium insure as the premium increase was way too high. I have two vehicles insured with them, and the premium is R5460. I have small hatchback and a bakkie on insurance with them. I joined discovery insure in 2014, and I used to pay R1500 for the small hatchback. Now they tell me that my premium deserved to be over R 2100 for this 6 year old vehicle. This is ridiculous. I hardly claim, and I am still penalized. The bakkie starting premium was R 2400. Now the insurance is over R 3200 in over a space of a year. This is utterly ridiculous. When I wrote to them, their response was that they can't do anything to reduce my premium. I should be satisfied with the fuel cash back that I get if I use my rewards card when filling up fuel. This is a slap in the face for being with discovery for so many years. I have been with discovery for nearly 7 years, and this is what I get. I work from home most days in the week. I only go to the office once a week, but this is not even considered. How am I huge risk, when the car is always standing, and I only go to the office once a week.