Bad Service/Attitude Rendered and double Standards of warranty policies

I would really like to put in a complaint about the service rendered to an elderly client of approximately 70 years old, Mr Jan Esau. The client bought a Jebson JB108OU car radio player on the 20th December 2018 ( 12 month repair Guarantee) and was assisted by Freddy sekmutlo. The goods were given to the client without being tested in-store and without thoroughly explaining the warranty policy of the shop since the client is a pensioner, not really understanding English although the till slip was printed in English with the statement " PRODUCT TESTED". On the 13th January 2018 the client asked me to install the radio and I immediately accepted as I have been installing, and repairing car sound for the past 25 years. Before Installing the radio I supp**** it with the required 12V from the car battery but the radio did not switch on and so I stopped immediately, packed the radio in its box and asked the client to take the radio back to the retailer. When the client took the radio back, the manager was so disrespectful, rude and unprofessional towards the pensioner client and the manager asked the client to call the Technician who installed the radio and its when I went with the client to the shop. On my arrival, I tried to reason with the manager but she was very rude and unprofessional....as it was that her word was final. Since as I was not a Registered VAT Installer as per the warranty policy which was not explained to the client in an understandable Language at the time of the purchase, she said shoved us away with her disturbing racial attitude as if we were non-existent. But what disturbs me most is that the product was never tested in-store before it was given to the client but the till slip states otherwise.... Can you please intervene as I am really disappointed with the Upington branch.....most especially a service rendered by the Supervisor/Manager.