We have some customers who have taken our car out of state and stopped paying. What recourse do we have on them? The balances on their accounts are over $5000. Can't this be considered Grand Theft?

You will need to give more detail.

Is this a rental car?
Did you sell them the car?
Are you a private seller?
Are you a new or used car dealer?
If used dealer, are you doing the buy here/pay here option?
How did you come about selling them a car without getting the money for it?

Grand theft starting amount goes state by state. Or it might be called a certain class of felony theft. But if they are on the title, you just have a lien and have to go to civil court to get a judgment for that.

Odinn asks some very pertinent questions, the answers are needed to fully help you.

If you have a lien on the car, its not yours, its theirs subject to the lien. So theft is not an issue.

If they defaulted on a payment arrangement with you then you need to read the contract you have with them for your rights to repo. Some car sales give repo rights to the seller without the need to go to court.