Poor service and business ethics

Phoned for a quotation on a WiFi controlled smart inverter aircon. Received the price, thereafter received a written quotation a few hundred rand higher that the telephonic quote. Queried the cost with Jason, and got sent a new quote for the same amount as quoted over the phone. Paid, received the product and had it installed. Only afterwards did I realise the product was actually changed on the invoice to a different product. Was told there is nothing they can do about it and I should check my orders better. (In case they change it behind your back)