Pool repair settlement correspondence

On 17 December '15 a pool repair job was quickly and well done at my home. This turned bad when the manager/owner reacted in a hostile and irrational way when I queried the shocking high price invoiced and requested a review. Expecting about 70% less based on similar services recently provided - all under R1000, I stated my affordability right now (though not the real issue). This is the response I (a professional engineer) got