Excess increased by 151% WITHOUT PROBABLE CAUSE

I was going to let it go and keep my mouth shut about Auto and Generals excessive annual increase. My policy went up because I moved by R40 it then went up again by R40 due to my annual increase, the shocker came when I looked at my excess which had increased by 151% to R8850 - Now, when I asked for a VALID reason for this increase, I was told its so my policy instalment could remain as low as possible - now a cars value depriciates, and I have had my license for 12 years, fully comprehensive incurance for 3 years, I have NEVER claimed insurance nor been in an accident so there was NO probable cause.