When students or recent graduates come to talk with Anthony M. Sozzo, an associate dean for student affairs at New York Medical College, about repaying their federal loans, he sometimes struggles with what to tell them. He states that the answers are increasingly being complicated by an ever-expanding federal loan-servicing system. The number of entities that service the loans owned by the federal government has risen sharply over the past several years, from one company in 2008 to 13 as of this month. Keeping up with the increase in servicers has been a challenge, financial-aid officers say, and at the individual-borrower level the changes are causing confusion over what borrowers are expected to pay and where they should go to manage their loans. With 13 companies now handling federal direct loans and more to come, aid administrators predict that the resulting inconsistencies will overwhelm borrowers.