Except for the amount of the debt they seem to be within their rights. You certainly can ask for accounting. Incidentally why don't you file a BK?
As to whether the debt collection practices are within the law, you can google and read the Fair Debt Collection Practices Act. If they are violating it, then report to cops, Federal Trade Commission and the Department of Consumer Affairs of your state. Also, get an attorney involved to send a cease and desist letter and have all contact be made through him/her. This attorney can look into the legitimacy of the underlying debt as well.
Now, with respect to HOAs, this is what you should be aware of: the HOA dues run personally to you because the contract (the CC&Rs is between the HOA and you personally). Therefore, you continue to be legally liable for them even after you walk away from the house and move out, even after foreclosure, until the lender sells it to a third party. That is when title is no longer in your name. Also, per the CC&Rs, you are liable for any attorney's fees. That is probably the reason the debt is so much larger than you thought.
Get a consultation with a debtor bankruptcy attorney.
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