Prolog returns variable name instead of value

I have a method which checks where to place the next brick while building a tower.

freePosition(POS, LEVEL) :- levelWithSpace(LEVEL),
                            freePositionOnLevel(POS, LEVEL).

This method checks for a level with space and asks for the free positions on this level. In my case it should return two results:

• POS=1, LEVEL=2
• POS=2, LEVEL=2

However it returns the following output:

?- freePosition(POS, LEVEL).
POS = 1,
LEVEL = 2 ;
POS = LEVEL, LEVEL = 2 ;

How can I change the behavior that it returns POS=2 instead of POS=LEVEL?