If they just left you hanging with no communication they may be out of business. You might contact your Louisiana Secretary of State as many states have registration systems for collection agencies. If they are out of business, hopefully they were working on contingency and you can start over with another company.
If they actually collected money and didn't tell you, then that's another story. In that case, you'd want to talk to the district attorney, attorney general, and ftc to try and get someone looking at the matter (but don't jump to conclusions, because that's a serious allegation). Good luck.