Player name change

Hi! I connect my account to facebook today and asked me if i want to overwrite the save data on it and i press ok and after that when i login back my player name have been change but my rosters of characters are still the same but i loss my ranking to all events and my alliance. When i checked my alliance my old player name still there. How can i contact my alliance and is there's a way to get back my old player name. Can anyone can help me on this.