refused to exchange wrong item

I bought bolts with assistance of the sales guy who then gave me the wrong size bolts and I only realised that when I got home. I went back to the store for exchange and I met the same sales guy who still remembered me very well. He asked me \where the hell was I looking when he gave me the wrong ones". I went to the manager for assistance as I did not have the till slip but I had the debit card slip. He then looked at the amount and told me that he doesn't have time to retrieve slip for such a small amount. So I had to buy the new bolts. I did not know that we are valued based on how much we spend and that determines the kind of service one receive. Successful businesses value every single customer no matter how rich or poor. The worst part I built my house from scratch with cashbuild but today I am treated like a dog when I buy bolts. I am disappointed in the management skills as I myself am the manager and was not expecting such a low standard service from someone hired to manage and resolve customer queries. No wonder even staff members are so full of themselves. It starts from the management and spread down to staff."""