Bad service and attitude

On the July 11 2015 I went to Woolworths in Bloemfontein Waterfront to buy golf shirts for my racing team. I bought 14 shirts. Some shirts were priced at R150 some at R120, I enquired why difference in price of the same thing. I was told its a mistake as everything should be R150. I refused and asked to speak to the manager and she gave me an attitude that is how they work. And the store manager also came with similar attitude of take it or leave it. I felt I wasn't treated right as a customer. How can you buy similar item with different price only because someone made a mistake. The attitude of management was stinking to say the least.