Bosch Warranty wortheles

I have 35 years experience working with Power tools in my trade. ! Bought a Bosch Angle grinder GWS 700 from Buco Knysna. Within 2 hours of work it started making a noise that sounds like a dry bearing or a bearing turning in the housing. I took it to Buco Knysna but they said the warranty does not apply because I changed the plug to a SA standard 3 pin plug. If this is the argument for dodging the warranty commitment from either Bosch or Buco then this would sit on my tool shelf as the last Bosch product or the last power tool bought from Buco.