Sallie Mae Raised monthly payment for no reason Wilkes-Barre, Pennsylvania

Received a statement through my email for my monthly statement on my son's student loan. I don't look at it every month since I have an automatic check coming out of my checking account. For the last couple of years I have been paying the same amount. In september (for no reason I can see) my payment jumped from $286.91 to $352.38. I was not aware of this increase and if not for checking my email I would not have known of the increase. Now I am behind and am charged a late fee on my next payment. Of course when I was aware of this, it is after hours and no one will answere the phone. This is not the first time this has happened. Also in the last year my principal has only been going down my a couple of dollars a month and in the last month the principal has increased. So from what I can tell this loan will never be paid off, it will continue forever. I can't afford to make higher payments. Its either pay for my mortgage or pay for this student loan.