I'm a current student at Oxford and got my acceptance to the DPhil in Theology/Religion on Wednesday. If you haven't heard yet, I wouldn't stress too much. They don't release their acceptances at the same time. For instance, my friend got her acceptance to the DPhil a week earlier than I did. And when I applied for the MPhil two years ago, I didn't hear until the end of the first week of March. Give it another week or two at least. Hope you hear good news soon!