Excess jumps by 390%

Why does my excess increase by 390%? This is the second time MiWay does this! Last year they hiked my excess with 254%, this was without any claims or incidents. When I noticed this (only upon having to claim) and complained, MiWay 1st wanted to jack my premiums with 65% in arrears!!! This would have made my excess even more than the jacked excess, and my premiums would now be more than that of a SUV (for a 12 year old Fiat Palio). After running their numbers and a few comparisons which I mailed to them MiWay rectified my excess in October 2017. On rolls 2018 and today I receive my increase papers (Policy Revision) and lo and behold the excess of my Palio has jumped now with a staggering 390%!!! So this is how MiWay works: Want a lower excess? Double your premium, and next year they reset your excess to that years default. This is a low and reprehensible tactic!