Is my apartment complex letting me sublet even tho it is not allowed in my lease agreement?

In my lease agreement it states that they do not allow subletting. However, when I moved in I had to get a two bedroom because there were no one bedrooms available. I was the only one that signed the lease which is up in October. Before I moved in they told me that if I needed to get a roommate that they were ok with it. I had two roommates from December 2012 to April 2013 and I have a new roommate moving in this week. However, I asked the management if there would be any penalty if I had to move out early because my company is looking to transfer me. They told me that I would lose my deposit but that would be the only penalty. But I told them that they would still have my roommate that would be paying rent and that I could get a replacement for myself. They refuse to let me do this because they do not allow subletting. But am I not already partially subletting when they are allowing me to have a roommate who is not on the lease?