Cellsure is just ripping me off

I lost my S4 which i insured at Vodacom/cellsure and according to my Knowledge my phone was insured up to the value of R10000 and today my claim is approved for 7500 but my premium never changed and now I am forced to take my phone to the value of 7500, whereas I pay month to month an insurance to the value of R10000. I am sorry but that doesnt make sense to me, because if the value of my phone went down so should have my premium. I don't want the S5 I want something worth the insurance I am paying for.