There are a few different ways to mitigate radon. The most cost effective method involves cutting a hole in the basement (floor) slab and inserting a PVC vent pipe into the ground. This PVC pipe would then extend up through the house and attic and has a power fan that draws air through the pipe. This draws the radon with it and expels it out of the house.
Here are some Radon contractors.
Quality Radon Services
The Radon Guys
Leslie H. Mateffy III