Took my old S7 that was completely not working to the Samsung Repair Center (https://goo.gl/maps/h4SF2adj6ww) and had quick excellent service. I was expecting days or weeks for repair, but only took a few hours.
Within 2 hours they called me and told me the problem. I said fix it and they had it fixed within 2 hours. Replaced the motherboard and the battery >>> I had plugged it into a wrong outlet with a bad charger and fried the electronics.