Poor service from builders express South Gate value mall

Bought a DIY 150mm Ryobi grinder from them. After 2 weeks it started to vibrate viciously even those got the disc was secured. When I got to reception she was rather rude and abrupt and wouldn’t repair it under warranty that was due. I was told in no uncertain terms that I had lost the warranty due to the fact that I replaced the two pin plug with a three pin. This was not the first time she was so obnoxiously rude and I got my back up the third time I went to collect the grinder to repair it myself. She wanted me to pay another R104 to replace the bearing. The manager tri d to help but she denied emphatically that she was rude on two occasions.Doesn’t the warranty count anymore in this country. I will never buy from builders warehouse ever again.