I am not licensed to practice law in your state.
These comments are made for educational purposes only and do not constitute legal advice. No attorney-client relationship exists between us.
This may be an attempt to trick you into acknowledging the debt is yours. If you "apologize" for not paying the bondsman could use the letter as proof that you admit owing the debt.
Do not write anything other than a letter (certified mail) DENYING the debt and demanding proof of the debt. Don't make any explanations.
If you are serious about the identity theft, you should go to the FTC website, download the identity theft package and send in the notarized statement to the creditor.
That statement, sworn under penalty of perjury, should demonstrate that you are serious about the issue.