Telephone number was in CID.  Since I am in contact with DE agencies, called back.  Recording advised the customer service persons were with other callers.  Please wait for the next available caller and have case number ready. Asked for brother.  Advised them he does not live here.  Claimed they were researching.  Came back and apologized because it appears someone spoke with brother.  Confirmed that my telephone number would be disconnected from his name.  She claimed yes.  Blocked number anyway.
Spoke with brother.  He claimed he was up to date on all bills and he did not understand who was calling.  Warned him to be careful of extortionists.  I suspect it was a debt collector.