Girls on our Floor

My roomate and I live in Memorial Hall. We live at the very top, the 3rd floor. When we moved in, I knew only two people people on our floor. My roomate didn't know anyone, because she came from Indiana. We quickly made friends with about five or six people on the floor we didn't know. Unfortunately, about a week ago.. We came across some problems.
Girls on our floor like to take things off our door. We also have a dry erase board on our door, which they like to erase the things we write and write things of their own. Not only is this bitchy of them, but I find it down right disrespectful. This has been happening for about a week now, and if this continues, we plan to take it up with our R.A. Keep ya posted.