Man, I really love these idiots! Legal Mediation Practice, you never fail to amuse me. I am going to have to ask them if I can have a tour of their facilities some day; I'm dying to see what type of people work there.
Larry, I wish your bank would have told you to fill out and "Affidavit of Unauthorized ACH." This would have helped you out back then when the account first became overdrawn, as you had advised Cashnet not to attempt to debit your account. As it is, it's probably way too late now. You could check with the bank, I don't think it would hurt to go into a branch and explain to someone face-to-face exactly what happened. You never know. I'm also very surprised whoever you talked to at the bank couldn't use common sense and see the overdrawn balance was caused by the NSF fees from the attempted debits.
LMP is just trying to scare you, Owing money is not a criminal matter it is a civil one. The worse they can do is sue you for what you owe Cashnet and, considering they have alrady broken the law (The fdcpa) by telling you they are going to pursue criminal court action, I doubt that will happen.
Also, since the account was opnend at the time they attempted to debit your account, and was subsequently closed because they overdrew your account, I'm pretty sure you can't even be prosecuted for "passing worthless checks." No matter what state you live in.
I would send these idiots a debt validation request and a partial cese and desist letter immediately. Tell them you only want them to communicate directly with you, by mail. If you need examples of these letter, check out my posting right above yours and you'll find letter examples there. Make sure you send the letter certified mail, return receipt requested.
Also, please check out this site and register. There is a lot of good information here that might help you out.
Keep us posted as to how things work out for you.