Poor service

I bought prepaid electricity from Pick n Pay Birch Acres last month and when i wanted to buy it today I was told that the don't sell it. The cashier went as far as to tell me that I'm lying when I said I bought electricity there last month. The supervisor Naledi just said, yes we don't sell it as if I'm a sangoma who must automatically know when you stopped selling prepaid electricity. The staff is unprofessional, where the hell do you get the audacity to tell a paying customer that they are lying, telling me that electricity is no longer sold would have been better received than calling me a lair. Can you train your staff, the reason for purchasing close to home is convenience and I refuse to travel to "white" suburbs to receive the service I deserve in my local Pick n Pay., I've never received any donations from Pick n Pay and I deserve to be treated like a paying customer and addressed professionally