This is not my debt> How do I stop these people f

WHo are "these people"???

A DV letter or debt validation would be a good start.

Asserting an account not mine is obviously difficult, for it is asking you to prove a negative.
You can start with a DV if reported by a debt collector, but they are not the party with whom the asserted debt originated. They thus dont have the business records to make a determination. Also, the DV process is not a dispute process. All they really would be required to do is to state that, yes, they were referred collection by the OC, provide the name of the OC, and the amount of the debt.

The party with the facts is the OC. You are really shut out if the OC never reported their account with the CRA, since that would remove the ability to file a dispute with them for inaccurate credit reporting. If the OC has reported, that is where I would start. First file a police report, and use that (FCRA 603(q) calls that an "identity theft report") as some support for your allegation, It at least is considered under the FCRA as some support for the assertion that an account did not derive from any transactions intitiated by you. Include any other supporting documentation, such as inconsistencies in name, address, SSN, etc., or any conversations you have had with them relating to identification of the account. That gets your foot in the door as far as dispute on the merits.

In the interim, you can post a fraud alert to your CR under FCRA 605A, alerting others to your assertion, and you can file your identity theft report with the CRA under FCRA 605B, and get the reported information related to the alleged identity theft blocked from your CR until it is resolved,