Ridiculous Instakments

I have been with Platinum Life for more than 7 years now and I have never had a problem paying my installments up until this year. They tried to Increase my installment twice now to "keep up" with the current medical expenses. Both times i had to explain that it is getting ridiculously expensive and that i cannot afford to increase my installment so much every time. Just give an example. My Installment in October 2017 was R574.39 then in November they added the 10% yearly Increase, which took it up to R631.85. Then a couple of days after that I got a call to Increase the installment with another R170 whatnot, which I have declined due to financial reasons for the second time this year. This would have brought up my Installment to +- R800. This means should i have excepted the additional R170 whatnot my Installment would have increased with R225 + (39% of R574.39) within a matter of days. What I wan to know now is how do i cancel this and what is going to happen to ALL the money that i have paid over to Platinum Life over the last 7+ years. I chose Platinum Life because they were full of promises so many years ago, but now I feel like I am being taken advantage of financially.