MRS. BPO L.L.C You dont own my loan to collect on! Cherry Hill New Jersey

 Today is 7/15/2013 and I have recieved a second notice for collection on a student loan. I have tried to contact this company and am asked alot of personal questions. When I will not give my S.S.N they get angry and start screaming or hang up, I block my number when calling and they continue to try and get a number for me. The problem is I have told them they are trying to get a settlement on a loan that I am currently paying with a differant company. MRS BPO company says on the paperwork they send they are authorized to settle,  but ASA says they are not. They also say they do not report to credit agencies but they are showing up on my credit report. Luckily they don't have my number, cause if they where calling me nonstop, I would have bigger problems. Is there anything I can do to get them off my credit report and to stop sending letters?