Excess increased by force but my premiums stayed the same :(

I received an updated policy schedule for my car insurance and then I found that they have increased my excess amount without calling to let me know. I called them and they gave me some lame excuses as to why it was increased. One of them was that they have managed to fulfil other customer's claims, I mean what does that have to do with me, I have never claimed at all since my policy commenced 4 and a half years ago. According to my knowledge, excess is linked to premiums, the higher the premiums the lower the excess and vice versa. So now they increased my excess but my premiums stayed the same. This is daylight ******* straight!!!