I am sure my student loan consolidator made a mistake and the total is more than i should owe,?

I consolidated my loans when I was still going to school about four years ago i consolidated three times with the same company, i was looking at my records on the nsds and im sure a mistake was made between the first and second consolidation, as suddenly there is a difference of more than five thousand dollars between my actual loans, and the consolidation total-and 90% of my loans were subsidized, so interest couldn't account for five thousand dollars. after that second one, my loans got consolidated one more time, now my loans are being held with yet a different company, and this company just tells me they have nothing to do with it, i need to take it up with the company that reconsolidated, i don't feel that's my responsibility, for one thing-and what good would it do anyway? If the company who has the loan now doesn't want to check it's history and seems happy to hold me accountable, is there any kind of law or some process I can initiate on my own, that would determine liability