Having experienced the situation Kostja described, I prefer
not to move towards a coach to explain a call, ever. I report the foul first (this usually allows him to cool down a bit), then I either give a brief answer (it may be something like "he doesn't have to be stationary" in a block/charge situation) while already moving towards my new position or I ignore him completely.
Unless there are 5000 people in the gym, you should be able to talk at a distance... and it is advisable to do so
