Dishonest motor spare franchise and franchisee

Went to buy spares from Benoni Midas and asked for a discount which I normally get. Was told the discount was already included in price. Looked at old slips and saw discount was not included, when I phoned to complain, I was told there was a new software package with teething problems and no discount could be given . So since 1 March 2018 they have been overcharging people. Then they say sorry but cannot rectify. Head office phones me back and says to me, they charge a reasonable price for a product and no discount has to be given. But the motor spares industry has been known to overcharge and offer discounts, so now you have a dishonorable franchise with a franchisor to match. Look at other spares shops that are more honorable.