38% increase in 3 months????

I am really unhappy with Santam, I recently bought a new house and got a quote from them to insure my building. The quote came in at R386.08, less than the banks insurance of R408. It however took a few months to register our bond as we were held up by building plans. A few months later when I advise Santam that the house has registered and to activate the insurance on the building the amount they are deducting is R530.86 - on exactly the same house a 38% increase???!! The excuse a quote is only valid for 30 days. Why have my credit score suddenly diminished, please can someone explain to me? I have been a loyal customer for many years but is extremely unhappy about this situation and would like someone to explain to me how this is possible. In the mean time I will get quotes from other insurers to consider moving all my insurance away from Santam which includes: Building, Home Content, 2 Cars, 2 Cell Phones