get more information about the bill collector. If its not a direct creditor, but a actual collection attorney or agency, fax them or mail them a Cease & Desist letter telling them to never call you again in accordance with the FDCPA [15 USC 1692c] article 805
(b) COMMUNICATION WITH THIRD PARTIES. Except as provided in section 804, without the prior consent of the consumer given directly to the debt collector, or the express permission of a court of competent jurisdiction, or as reasonably necessary to effectuate a postjudgment judicial remedy, a debt collector may not communicate, in connection with the collection of any debt, with any person other than a consumer, his attorney, a consumer reporting agency if otherwise permitted by law, the creditor, the attorney of the creditor, or the attorney of the debt collector.
(c) CEASING COMMUNICATION. If a consumer notifies a debt collector in writing that the consumer refuses to pay a debt or that the consumer wishes the debt collector to cease further communication with the consumer, the debt collector shall not communicate further with the consumer with respect to such debt, except --
(1) to advise the consumer that the debt collector's further efforts are being terminated;
(2) to notify the consumer that the debt collector or creditor may invoke specified remedies which are ordinarily invoked by such debt collector or creditor; or
(3) where applicable, to notify the consumer that the debt collector or creditor intends to invoke a specified remedy.
If such notice from the consumer is made by mail, notification shall be complete upon receipt.
(d) For the purpose of this section, the term "consumer" includes the consumer's spouse, parent (if the consumer is a minor), guardian, executor, or administrator.
if they continue to call you can file suit in your local federal court against them for $1000 fine per time they violate it. Either they violated 805(c) and call you after a C&D or they refute that you are defined as a 'consumer' iaw 805(d) in which case they, under oath, admit to knowingly 805(b) and continue to contact you as a third party. Either way its $1000 per violation opting for 813(2) under civil liability.