Complaint Review: Cash Advance Services

I have received phone calls and emails demanding that I pay over $800 for a $300 loan they say I took out in 2013. 

When I demanded a bill or statement via email to prove to me that such a loan existed, the caller (who had an east-Asian accent that was very difficult to understand) hung up on me.  They sent me a "bill" via email the next day saying it was from Cash Advance USA, 320 NE 8th Street, Homestead, FL  33030   Phone # 347-402-1512.  (That area code is from New York, which is where the phone calls I've received from them on my cell phone register as being from--not from Florida.)

The caller's demeanor is very threatening, rude, and unprofessional.  (What "bill collector" hangs up on you?!)  The emails threaten being taken to court in a matter of days.  I've encountered callers with similar accents in the past who were not legit, which makes me very leery about fulfilling this caller's/emailer's demands.

I have sent no money to date.  I wish the threatening calls and emails to stop.