First, reduce the amount of fertilizer they apply on their lawn. Most fungus grows better in a nitrogen rich environment. Second, step make sure you are not over or under watering your lawn. Both can stress the grass. Last, apply diluted dish soap to grass to kill fungus spores.
All you have to do is resod the area. Or, you can reseed it, but that might take awhile. Once you have healthy grass growing, the fungus won't be able to latch on and grow. Make sure your lawn has adequate drainage, too.
try using vinegar its a acid so it kills a lot of plants but its not a very strong acid so it wont kill your lawn just put it in a spray gun and spray your lawn for a few days. then water your lawn after the fungus is gown to get rid of the acid