MFC extend my contract term to 61 months

I took a car loan with mfc back in 2010. The installment commenced 27/10/2010 and the final should be 27/09/2015 but now they have extended to 27/10/2015 this will extend my contract to 61 months. I have never skipped any installment and am not in areas. they give an excuse that they reduced my monthly installment in 2012 which i disagree. the reason my installment was reduced by R100 + is that interest rate went down in that year. i signed a fixed contract and the installment will only change when the interest rate changes. they claim that my account was in advance and a restructure was done to reduce my capital which reduced my monthly installment.<br> <br> Shame on you MFC, your service it totally unacceptable and we call it day light *******.