Misrepresentation of Zero Excess for low mileage

I have had insurance with Alexander Forbes since 2015 for householders, building and vehicle. I am unmarried aged 60. I have a 2008 Renault Clio with 83,000 mileage. I was informed in 2015 that I would qualify for a discount due to my age and a "zero excess" due to low yearly mileage. My last insurance claim for an accident was in 1997 which was not my fault. Since my insurance with policy with Alexander Forbes, I had a claim for a crack in my dining room ceiling in late 2017. A structural engineer was employed by Alexander Forbes to determine that my claim be rejected due to poor construction some 15 years ago when the dining room area was built. I bought my house in 2013, so this was a shock to me. I had a further claim in January 2018 for my car after a gate was closed onto my car when exiting a property. I was informed I was liable for an excess of R5000 for the repairs as I had, in their opinion, exceeded my "zero excess" on mileage. I had an unfortunate accident in the road I reside in when I turned the corner at the stop street and lost control of my steering wheel, hitting a street pole some 5 houses away from my house. Since last week, I have been subjected to instence interrogation by private investigators to determine whether I was intoxicated, reckless or negligent when I hit the street pole. My airbags did not deploy, so I would not have been travelling at an excessive speed. The private investigator has asked for phone numbers of my security company, friends and neighbours to also interrogate them as a way of repudiating my claim, for whatever reason, in order to prove my wrong doing and lack of integrity. I am comprehensively insured for theft or accident and this is what is was, a devastating and unfortunate accident after I have looked after my car in all these years and just in May had the front tyres replaced and exhaust and serviced my vehicle annually. I feel Alexander Forbes have totally misrepresented themselves to me, the insurer, in the event of an accident or a legitimate claim, especially related to my "zero excess" for low mileage and the fact that I am a responsible driver of 60 years of age, having never been prosecuted for any misdemenours in my long driving history. Since Wednesday, I have not been contacted or informed as to whether my vehicle is repairable or a write off and am extremely concerned as to what my excess will be in the circumstances.