So, What I can do for you?

I served a customer with weird attitude today. It was one of the worst customers I ever met. Dealing with people like this. A customer who walked in and asking for wholesale price of soldering tools but taking few quantities. He told me that he have previously bought these at cheaper price compared to the prices I currently quoted him. He refused to show me the receipt of his last purchase and saying that I could give many reasons not to follow the previous prices. He even refused to tell the date of purchase being made. I repeated many time, saying that if he could show me the receipt that have the power to convince me to give him such lower prices, I will definitely allow the discount. But, he was so freaking stubborn and declined to show. I could not really understand why it is so hard for him to provide an evidence, I wonder even the boss of company was not allowed to view the receipt? Why he wanna act so fucking mysteriously? Dealing with people like him, requires me high level of EQ, most of my colleagues also beh tahan him, keep beating around the bush, yet he is willing to buy with the current prices instead of walking out and entering other shops. I said that I could not do anything to help if he insisted. 'Suka hati u la, u mau bagi saya untung lebih banyak, saya tak kisah punya, janji u hapi la...' that is what I can say to him...