On Line Payday Loan Lender is Threatening Fraud

They cannot sue you for fraud unless they have evidence that will prove that you actually did commit fraud. This is a typical tactic some payday lenders use in order to scare you into paying.
The first thing you need to do is find out whether any of these payday lenders are legal in your state. If they are storefront lenders then they are most likely legal. In Indiana the Department of Financial Institutions regulates payday lenders.

No, none of them are legal in your state, CLICK HERE to find out how to deal with illegal lenders.

I did everything that was suggested regarding the default on my online payday loans, closed my account, sent the cease and desist letters, filed complaints with Indiana attorney general's office, FTC and BBB. I also filed a complaint with the Delaware Office of The State Bank Commisoner against Nationwidecash.com (they have assigned an investigator). After all of this Nationwidecash.com is still calling my cell phone and work numbers. Arrowhead Investment responded to the c&d by stating that I waived all rights when I electronically signed the application, so the c & d letter does not apply to them...is that right? They have threatened to sell to a 3rd party collection agency and report to the credit bureaus!

How do I get these people to stop harrassing and threatening me? What more can I do? Can they do everything they are threatening?

They can't get you for fraud, and if they report to the CRA's all you will need to do is dispute it on the grounds they aren't legal lenders. As far as the calls, the more you talk to them, the more they will call, so, you need to hang up immediately when they call. They want someone to argue with, don't give them that.

Honestly, it would not matter if you had paid them back or not, they would STILL call you and claim you owed more and more and more. The thing is, you are a victim here, so you need to explain this to your employer, also inform your employer that you have done everything within your power to stop the harassment, but you can NOT control who calls you, or the number of times they call. I am sorry, but you simply can not stop them from calling, I wish you could but it just won't happen. They will eventually give up, and may start again in a month or a year, they are criminals.

You may want to consider getting your cell phone and home number changed.