ABUSIVE BANK, NISSAN CORPORATE ACCEPTANCE?

Someone please advice me on this... My husband bought a car last year which he could afford at the time but not any more, and got a 15% interest which makes his payments 800 a month for an 06 infinity, lately we have been making late payments since income has decreased and Nissan Corporate decided to raise our interest to 24% which is a ridiculous 500 a month just on interest!! besides we recently found out that they were charching us 12.88 PER DAY for late payments which is almost 400 for one month late! besides the extra $5 for late payment... I FEEL BANK RAPPED AND HAND TIED, i cant hold up much longer on payments, much less now with the increase, i have tried to sell with no success, if i do a trade in we will be in the same hole because we are already upside down, sometimes i feel like not paying and getting repossessed but i do care about my credit and my husbands... what can i do?