Sorry, but the interest should NOT be waived as its spelled out in the paperwork that you signed accompanying these types of loans.

For future reference, you should also amortize the loan yourself rather than rely on the amortization the company gives you.

Usually, they put a balloon payment on the end of these loans to catch you off-guard. If you amortize the loan yourself, you can then ensure that every monthly payment you make will be the same (including the final one) and you won't encounter any nasty surprises at the end of the loan.