Standard bank Homeloan insurance

Hi I have an existing Homeloan with standard bank. Last month I app**** for a further bond to do renovations at home but I cancelled when I was told I need to pay attorneys fees so now to my surprise the structural premium went from R500 to R3000 I called the insurance department to explain to me why it went up they are telling me because I had app**** for a further bond they did an aerial inspection and the value of the property moved from R2.4 million to R4mil due to a thetch roof but when I bought the property it was still a thetch roof. I feel like this a day light ******* how do they increase my premiums without my consent. I didn’t authorise anything or sign any document stating change of premiums. Tomorrow they are going to debit R3000 from my account I’m furious I want my premium to go back to R500