No water pressure in your house? Do you seem to have pressure a few days and then it is gone again?
First if you have a water softener put it on by-pass. Then check to see if you have normal pressure. If the pressure went back to normal, yes there is problems with the water softener. If the pressure did not get better call the water company.
Do you really need a salesman to come to your house to determine what you need for a water softener? The answer is yes and no. A educated water softener company will already know the approximate hardness of your water. Every time a company installs a softener they test the water.