Singles pay a higher premium than married

For the first time in 12 years I received a call from Outsurance checking my details. When asked if I was married or single I said single. I was told my policy states married. I explained I have lived with my partner for 20 years and as far as I am concerned he is my common law husband and I am as good as married. I was told as I am not married I would have to pay a higher premium of approx. R1500.00 a year. I responded by saying I consider this to be **************. As a woman with a common law husband does this make me a worse driver than a married woman whose husband may have any one of a number of problems. I find this quite unbelievable.