Nedbank Home Insurance

I need advise regarding home insurance, I bought my house about two years ago, recently my geyser burst damaging three rooms in my house, my insurance paid out an amount to get my own contractor to fix my geyser, I then asked the same contractor to do a quote in order to fix the three rooms that was damaged due to the burst geyser, (ceilings, carpets and walls) the insurance then only want to pay a forth of the amount that was quoted to repair the three rooms due to the house being too old and not maintained properly. So my question is why do they offer insurance on your house even if they knew in what condition the house is, so now when you need help due to a geyser that burst, they conveniently blame it on the house being too old and not maintained and says you have to cover the rest of the damage expenses. Can anyone kindly assist, my contact number ***