SunTech Loan (sold to ACS)?

Got some paperwork that makes it appear that I have been doing nothing but paying 'interest' on a SunTech Student Loan (until it was sold to a company called ACS); got 'new' printout of what I am to pay for the next 102 months. WTHeck can 'anybody' tell me about what is going on. Son has received same paperwork when he had been paying CHASE, with 'extra' payments (with coupon book) and also with a new "Loan Consolidation Disclosure Statement and Repayment Schedule" ... where has our money been going for the past 7 years? Who do we contact to try to get answers? All I get is someone with a 'foreign accent' who tells me, 'oh, it be the "audit" ... you haffa pay the loan now, money is now gonna go to pay off principal.' IT SHOULD have been going towards the principal more than 5 or 6 years ago. I want some ACTION and some answers PLEASE. Sounds like we are being 'royally' screwed (excused the pun).