Mr.Pnkaj , please follow the steps.
1)You have taken a loan of Rs.4,000/- in 2006 @ 11.75% and has not paid any amount till 2010. Assuming that the interest even with simple interest you have to pay Rs.2 lakhs per four year and the outstanding amount have been Rs.6 lakhs + and the instalments you have been paying is barely sufficient to Rs.72,000/- per annum interest, and at this rate you may not be able to repay the loan.
Find out the RBI /IBA directives on education loans and they are uploaded in both websites of IBA and RBI, search in google with key words Education loans RBI/IBA directives.
Handover the details of transaction to any accountant and let him generate a statement with agreed interest (Simple during education, compound after that or as stated in RBI directive.
(Believe me, after computerization there can not be such mistakes in interest calculations by banks, only for your clarification, I am providing this alternative)
Then you can find out whether Bank is correctly applying interest as per RBI directives, and correct interest was applied at the Branch.
If you find difference, make a grievance, enclose the directives and generated statement and report to Grievance officer of the Bank and as well to RBI.
If not, try to settle the amount through compromise. (As you have not paid amounts as agreed, Bank might have stopped applying interest as per prudential norms of RBI, not to apply or debit interest on Non performing advances)