2003 Subaru Outback Headlight problem

Hi I took my aunts car to the local auto parts store for a headlight bulb that went out. But the problem is that the high beam works and not the normal mode. I went ahead and replaced a new bulb and the same problem occurred. I am stumped on how to go about this repair. I am thinking it may be electrical but not sure how to trouble shoot this problem. Any help would be greatly appreciated. Thanks