If these are store fronts, which cannr says they sound like it then they are more than likely legal. You need to contact them to set up payment arrangements with them because they can will most likely sue you.
It is better to make the first contact with them so that they know you are willing to take responsibility for the checks. If you don't feel comfortable calling them, send them a letter certified/return requested letter giving a propsal with an amount that you are comfortable and can afford to pay them back, and a time line of how much time you will need.
I did this and my store fronts have been wonderful, I know that is hard to believe, but not all of them are nasty people to work with. Advance America was one of them.
Good luck and keep us posted.
ladybug