I would talk to the rental company and ask for an itemized list of the utility costs. I don't know where you moved from, but utility costs in this area can be much higher than other areas. You may very well have spent that amount and not realized it with the higher costs - just a thought...without the proof you are actually just guessing that you didn't spend that much. You also won't know the rental company is telling the truth without the proof either.
Sadly, I'm not sure you can do much about the trash left behind and being charged for it. It sucks and the landlord should have taken care of it for you, but you should have called and informed them as soon as you moved in that they need to clean up the place. I would definitely tell them about the trash now, but I'm not sure you'll be able to get a good solution at this point - should have done it in the beginning.
Good luck!