Replacing bath fan light heater - Existing Wire is (3) /2 cable
If you have 4 cables going into the switch box and the white wires are pigtailed together and there is a hot, black, connected to the common post,  then  connect your three white wires from the switch box to the three white wires from the fan unit. Then connect each switch wire to one of the wires from the fan unit. You can rearrange the switch locations in the switch box for your preference. Remember to shut off the power at the main panel before doing any work. 

In the future, don't just try all different combinations to see what works. Sometimes things will work but can still kill you..... Take pictures and come back to this site for help before you start. There are some really smart people (not me) that will help you out.