Return good not attended to

I bought a padlock in Jan 20th for my son's online learning. At Wonderpark branch. In February it started malfunctioning. I took back to Wonderpark in May since I stay in jhb. The sales assistant was not happy that I brought back. Since May till now I make follow up but they tell me they will comeback to me. My son is unable to attend online classes. I'm angry at how I paid R4500 cash for nothing. Incredible connection has bad customer service. I will make sure my family and people close to me never buy from them. Their competitors would have exchanged. U lost a customer and I need a refund. I wish I bought from Makro . Good customer return policy and efficient