I can tell you my car is financed with some of the biggest a-holes that walk the planet. And this worked for me when I was behind.
The best thing to do is call them and level with them and say THIS is what I can pay to you. THIS is what I can afford. You will have to stand very firm with them. And whatever you tell them you will do..DO IT. Don't overpromise them.
If you can't get a good answer from the first rep, try again.
Follow it up with a letter, outlining the details of your repayment plan. And most important, stick to it.
Citi Financial is known for being hard to deal with. You just have to be harder. Good luck!