Bad service at BMW Dalpark

I cannot even begin to express my disappointment with BMW Dalpark. My daughter's Mini Cooper somehow died (as in lights and everything went off) on Saturday (13/04/2024) and miraculously came on and hour and half later. It was fine since then but being a parent, I thought we'd have everything checked out for my daughter's safety. On Monday (15/04/2024) my daughter and I took it to First Battery Centre in Brakpan to have the battery checked. It was tested 3 times using 2 different devices, the battery was perfectly fine. They told us to take it to the mechanic and have the starter and wiring checked. The gentleman suggested that it might be that the battery contact might be lose and needed tightening. We went straight to BMW Dalpark and booked it in for Wednesday (17/04/2024) to have it diagnosed. A lady called me later that day to give me an update on the findings. She told that the first issue was the battery and that I needed to give them a go-ahead to replace it before they could carry on with the diagnosis. The quote was R9710.03. I was not about to pay that amount for a battery that I was told was fine. I then asked to fetch the car and pay for just the diagnosis. My daughter collected the car as I was in Heidelberg at the time. She called me, frantic with worry, and said the car was worse. It was switching on and off in the middle of the road and other cars were hooting at her. Thank God she made it home (3km from BMW) but as soon she parked the in the garage, it died. I called an auto electrician to have it checked out at home. We were shocked when he checked the battery, and found that the battery contact was loose which is what we were told at First Battery Centre. He tightened it and the car started. I can't claim that it was loosened at BMW as I don't have proof. How then, did they not pick it up during their diagnosis? And how did they come to the conclusion that the battery was faulty whereas there's nothing wrong with battery? This was reckless on their side and put my daughter on serious danger. I'm very angry and utterly disappointed!!!!