Poor quality parts and poor customer servicr

Bought an alternator from them in the 29/10/2018. Fitted the alternator to customers vehicle and it did not charge. Voltage reading if 11.9 volts. Contacted them and I was told to return it and they will gave it repaired. They contacted me on the Tuesday following and to me it was repaired as there was a problem. Keep in mind that my customer has only one car that he uses for business during the day and then travelles to his wife's restaurant in Springs to collect her at and take her home at 12 midnight. I then fit the repaired alternator, which to me is now second hand or as is the , it is a repaired unit. Start the car in all faith, and guess what, it still dies not work. They now say I must bring the car to them and they will get their workshop to see to the problem , but they are not prepared to assist my customer with transport. So to all potential customers of Gemini, I will not buy anything from them as their products are of inferior quality and their customer service is very poor