You CAN pay off your loan early.
There are no laws that prohibit a debtor from paying off early ALL or a portion of his note.
Read your loan contract, it's entirely legal, and the lender can't legally refuse your early payoff request.
However, the bank isn't required by law to allow you to renegotiate the loan.
You simply ask for the PAYOFF amount.
You then wire, ACH transfer, or send a check to cover the costs to the lender (or follow the lender's instructions),
I think you're confusing a negotiated settlement, refinance, or some other topic with paying off your loan prior to the original due date.
Some loans ave prepayment penalties associated with paying the loan off early.
You should read your loan contract, or inquire of your lender.
Those early payoff penalties are rarer and rarer today, but won't prohibit you from paying the note off early.
http://www.bankrate.com/calculators/auto/early-payment-payoff-calculator.aspx