Shoprite - Pathetic customer service by manager

I am disgusted with the customer service i received at Shoprite, the so called Manager : "Muntu" of ( Eldorado Park Ext 5 ) was so rude and has no way of speaking to a customer, he is a gangster and refused to assist my mom that is 73 years old as she needed to exchange a broken calculator they sold her as it was bought for my daughter (15years old) that lives with her mom and not close to me and my mom, we only see her weekends when she comes for church, there is evidence to prove that it was the last and probably an exchange due to being broken, as new stock arrived in different packaging and the box was freshly opened and still on the floor at cigarette counter preparing to be packed upon my arrival to request for it to be exchanged. I am soo upset as he said he does not care and will not change it, I promise I will take this matter further if nothing is done regarding the exchange and disciplinary measures taken against Manager : " Muntu " , it's not about the money but the principles. Muntu said I should tell his managers he refused to exchange it and does not care and mom that is very old to come herself and he still will not change it as he does not care. Shoprite Eldorado Park needs to review their staff members especially their Arrogant Gangster Manager Muntu