Vodacom Repair Denied!

My son's phone, a Samsung Galaxy Z Fold 3, is 1 year old and stopped working 2 days after the 1 year period - we took out additional insurance on the phone. Vodacom won't repair it because of a tiny scratch on the outside casing of the phone - they say that it voids the Warranty, even thought the phone is practically spotless except for this tiny scratch. The scratch happened about 10 months ago, but they insist that this is what is causing the problem! The phone has been well looked after and is still under contract for another year.