technically you should have follow the bank instruction's to make payment... anyway since you have made 'extra' payment it is also good to save interest charged on your loan (which is based on outstanding of the principle)... since you have keep track of your repayment why not pay until balance of 10k (or less or more, up to your comfortable level) and call the bank and ask for settlement and close the case??? which you will settle you loan with bank in less than 20 years (which is the original tenure)...