Horrible service and breach of Consumer Protection Act

The worst after sales at a company I have ever experienced. My wife bought a custom gaming PC from Evetech for my birthday just under 6 months back. She spent quite a bit on it. When I received it, I only used to play Dota on it and that ran perfectly. However, once I subscribed to EA Pass I tried to run NFS and that did not work. I thought it’s an issue with EA games. I then also downloaded Fortnite and CoD and both games wouldn’t run. I tried multiple things to fix the issue and even factory reset the PC to no avail. The task manager would also crash when I would try to force close the games. I then sent it in to Evetech to try and fix it. They responded by saying they found an issue with the SSD and its speeds being slow and have replaced it. I was a bit surprised since I did not really think it was the issue. When the PC got back, I had the same issues as before and in fact it even stopped running Dota. I then sent the PC back to Evetech and told them that I want a refund for it since it’s within the 6 months that I have with the CPA. They have now responded to say that they cannot find any fault with the PC and that if I want a refund there will be a 20% handling charge and I must provide them with the packaging for the PC components. They make it seem like I am a **** and that there is no fault with the PC. Worst company ever. Anyone knows how to lodge a complaint with the Consumer Protection Act? I have the right for a refund since they could not find the fault and the PC is not working as intended to. Wish I could give them 0 stars. The whole team has bad service and try to put you into a situation where you have no option. Please help!