You can file an affidavit of fraud if you maintain that you never cosigned this loan. If your ex made it a habit of such behavior I suggest you check your credit report carefully for any other strange activity. Often where there's smoke there's fire. You may want to confer with a local attorney.
Disclaimer: The foregoing answer does not create an attorney-client relationship with Attorney Cannella or her firm. This answer does not constitute legal advice, is provided for informational and educational purposes only for persons interested in the subject matter, is not legal opinion, nor confidential in nature. Each situation is fact specific and may be subject to state specific laws. Without a comprehensive consultation and review of all the facts and documents at issue it is impossible to evaluate a legal problem fully.
Since you wrote a dispute letter, I would check your credit report and see if the debt is noted as disputed. If not, you may ghave a claim against the collector under the FDCPA. I don't see how an affidavit of ownership proves that you co-signed the note. You should seek the counsel of a qualified consumer attorney in your area.
Under the Fair Debt Collection Practices Act, you have the right to dispute the debt and tell the collection agency you do not want to be contacted. You should tell the collection agency you believe you x signed the card application. Also check your credit report. If you are sued by the collection agency be prepared to promptly hire an attorney and defend youself. Good Luck
The answer given is for informational purposes only and does not constitute legal advice. Dwight Bowen is a bankruptcy and consumer attorney and may be contacted at (404) 880-3310.