Damage - Consumer Complaint for INCREDIBLE CONNECTION - HEAD OFFICE

I took my machine in two weeks ago with a complaint of a strange happening occassionally for a diagnosis to avoid more damage. The tech said it was just the harddrive, we booked it in the prices were absorbent just for labour alone. All was paid upfront. He took out a 1t and replaced it with a small one !!! My work IT informed me when I called them because it was actually even worse and they checked it that the one they put was faulty. It was still functional. I requested they return it to its original state which he did and I went to collect it only to find when I tried to check and switch it on in store it was totally dead. It's been three days with no solution the tech says it was already crashing and I need to purchase Microsoft as well as a whole lot of other issues that were not there. My Microsoft had expired but was fully functional I am not a tech but I'm no idiot. They are unable to fix the error .