The terms of your mortgage are spelled out in the mortgage agreement. In that document you will find whether there is any provision to increase the interest rate if you are not paying as agreed. If that language is in there, you have no grounds to complain that they increased your rate. If it is NOT in there, you can take this one to court. At this point, it is a small claims court issue...cost under $100. The best final solution is to sell the place to your son if there are no better offers.