Hi Lynn
Welcome to the forums.
It might have happened that the debt collection agency has mistaken someone else's identity with you. This is quite acceptable but the situation worsens if the agency does not back up after pointing out the mistake. At this stage you should exercise your consumer rights as per the fdcpa law and keep them away from you.
Ask the company to validate your debt as it is your legal right to know the complete details of the accounts. If it is a legitimate one, they will be able to give you all the necessary information. Otherwise, you can take legal actions against them if they report negatively to the bureaus.
Give your letter the most legal importance and it should be clearly stated that you refuse to pay it unless you are served with the necessary details. Also, do mention that you refuse to be contacted at phone during this period and all correspondence should be done only through mail.
Violation of any of the mentioned federal laws will put you in charge of filing a class action lawsuit against them. You might be interested in recording the telephonic conversations for gathering legal proof. Later, you can show it to your lawyer for further guidance.
Lynn, do send your letter through certified mail with return receipt requested. This is most important because you will have a proof of every action made. This will also ensure that they have received your letter and it was their turn to give you the necessary details.
I hope that after you have exercised your legal rights, the debt collectors will stay in the best of their behavior. Please do keep us posted with the latest.
Regards
Roxette