Having your radon test performed in a rarely-used or unfinished basement may not present accurate results for the entire home. Oftentimes, the main living area of the home is tightly sealed with plastic covered insulation which can easily trap air. The ability for air to move more freely in the basement may show lower levels of radon than the rest of the home.
If the first test was conducted in the basement, consider a second test in the main part of the home. An unfinished basement cut off from the main house and is not an accurate representation of the presence of the radioactive gas in the living quarters. A second test can provide you with an accurate reading whether high or low.