A single phase 120 volt device needs a neutral line, a hot line and a ground, where as a 220 volt device only needs two hot lines and a ground in most cases. So the questions is did the electrician pull a neutral wire with your original 220 volts? You will need to replace the receptical and wire accordingly if you are going to try to plug in a 120 volt device. If you are going to use say a 20 amp 220 device on your existing 30/50 amp receptical you could have an adapter cord made up with the proper plugs and receptical and use your existing receptical.