I used the suggested above and sorted out the problem.
The issue around NPV is also to account for when the payments is made in the beginning of the (monthly) period or at the end of the (monthly) period. To be quite honest i do not trust the NPV formula on this stage.
It is easy to check it and that is to build an amortization schedule on the input and results of the NPV formula. The theory is that the balance must be 0 at the end of the period. But is does not.