Hot air instead of cool air coming from A/C on 2006 Ford Taurus

First I had a problem with cold air blowing out when I put the heater on, checked the coolant,it was low so added coolant, then heater started working and is still working..problem now is,when I put the air conditioner on, I have heat coming out instead of cool air, any ideas as to what may be causing this problem?

Asked by for the 2006 Ford Taurus