Portfolio Recovery Associates The numbers vary and I was told there were many offices and no "main" office. Said we need to pay ex-wife's debt although we supplied paperwork or we would never have credit, Georgia

This is about the worst possible collection agency you can be dealing with.
Send/fax them a letter via Certified Mail + Return Receipt (do NOT use regular mail) stating:

Per the Fair Debt Collection Practices Act, cease all communications with me. Receipt of this letter is officially being time stamped via Certified Mail.

http://www.budhibbs.com/cease_comm.htm

When you got your divorce what your attorney should have told you (and your ex) is that a divorce decree does not excuse either of you from the debts you incurred during the marriage. Both of you are still responsible for the debt.  If neither of you pay it will harm both of your credit.  What you would need to do is pay the debt then take her to court and try to get your money back.