Debt verification

I would send them a certified letter telling them that this is the last you expect to hear from them, unless they want to be sued by you for fdcpa violations. Since they have shown that they cannot validate this debt, in accordance with section 809 of the FDCPA, they cannot continue attempting to collect on this debt in any way, shape, or form. Since they keep trying to stall around their obligation to validate, my money's on them not being able to. An indefinite stay means they are withdrawing their claim from arbitration, indefinitely. They cannot legally answer your validation request, so they know they cannot continue.

Of course, what will probably happen is that they will either quietly try to get a default judgment against you illegally, or they will simply sell it to yet another junk debt buyer, so be prepared. It wouldnt hurt at this point to keep an eye on your county court clerk's office every once in a while to see if they have filed a suit in court there, just to be safe. I doubt they will because they know that you will use the validation card, but its better to keep on top of this.

Hell, I might even consider contacting NAF myself and saying that you want this ended now, because they are required to provide validation and they cannot do so. No validation means they havent met the burden of proof that is upon them.