I too have similar issues. I did my MBA from IIT Kanpur in India and my concentration was more of marketing. It was because we did not have a major in Organisational Behavior. My work experience also has Marketing Research experience. Now I see that I am more comfortable and confident in Organisational behavior topics. I guess as long as you show you are very focussed on organisation behavior that should be fine. You should not give them an impression that you are choosing it because it needs less math.
And we will have to do our course work anyway. So we would be comfortable with math once we complete those courses.