Listed for Unknown credit

MBD is listed on my credit report yet they have nnever sent me any Communication about it or even call me. i tried calling several times to find out what is it for and they cut off the line everytime they transfer to customer services. I left my details with the receptionist to get someone to call me back and still haven't heard anything frim them since last week. This is so annoying! How can you black list somr and not even make them aware of what that credit is for? I even sent two emails to their emails and still there's no feedback.