Samsung Galaxy S II :: Screen Broken - Automatically Fault According To T-mobile?

My beloved Galaxy S2 is currently with T-mobile for assessment as a result of a broken screen (under the glass) and the view of the shop was that as it was a broken screen it was automatically my fault.I am at a loss as to how they can know this without even seeing the phone. Hence why I was unprepared to pre-authorise a repair without knowing the cost first.I have no issue with paying if it is my fault (like I did when I put a phone through the washing machine or when I dropped one on a sharp stone and shattered the screen or when I left one on the car roof and drove off only to see it bounce in the rear view mirror!) but this time it was very different as the screen went black as if power had gone and it needed to be switched back on - i initially thought it was a power fault. The next day I discovered a crack in the screen.