I believe that Hinfarm was planning to pay extra on principal only. That is how we always did it, many times we had to call the bank when the statement came out...it seems that the teller's normal practice would be to apply any extra money paid to prepaid interest. They would sometimes even do that when we paid in person and instructed them to apply xx amount to principal.

We are out of debt now, when we had loans we always paid extra, every single month. Some months it wasn't much, but always something. We ended up (finally) getting 'special' treatment at the bank, when we came in to make a payment the tellers would get out their cheat sheet to make sure our payments got credited properly.