Raised my car premium by 25%!!!

I received my annual insurance review in Oct and noticed that 1 of the cars on the policy received a whopping 25% increase, whilst the other car on the policy received a 12% increase - still more than what I perceive as being the norm. Both our household content as well as building insurance also automatically got increased by 10% - even though both are already over-insured by more than 10% - so I obviously didn't want that either! I then e-mail Discovery Insure back to inquire about how they get to these ridiculous percentages (noting that we haven't ever put in any claims on any of our insured items with Discovery Insure!), after which I received a call from one of their agents who basically only told me that \their system"calculated our new premiums - I then told him that that was not a good enough \""explanation\"" and requested that he get one of his managers to contact me and give me a detailed explanation of the calculation - so that I at least can try to understand their logic for future references. However I never heard from anyone at Discovery Insure again and they obviously went ahead and deducted their newly calculated premiums from my bank account via debit order!!! """