It is a collection agency at 866-472-8762 goes by the name of ENCORE or Encore Capital Group Collection Agency.the website site for them is http://www.chargeoff.net
I suggest that you file a complete with http://www.consumeraffairs.com/, the Federal trade Commission http://www.ftc.gov/bcp/consumer.shtm and anyone ells you can think of.
for their rude and intrusive behave that is most likely supported by the company’s business practices