Ok, just did a little more research. I searched the number on Google maps and got a result for anyone who had problems. After the search, a place called bbyo came up near Inglewood. It looks like some sort of Jewish community. They have a website at bbyo.org in case you want to find out how to contact them. Unfortunately calling this number does not work. Good luck!
424-646-3921 belongs to a company named Receivables Performance Management a/k/a RPM. They are a collection agency located in Washington State. This is the information that I got when I called the number back. looking at the many comments below, it seems that they may very well be violating the TCPA (Telephone Consumers Protection Act) by calling your home or cell with an automated dialing system. If they are, you can make them pay you for your hassle (somewhere between $500 and $1500+ per call). Keep a record (notes) of when they call and what they say if you want to try to make them pay you. Look it up.
Here is a link to the law: http://www.law.cornell.edu/uscode/text/47/227
It is an easy read. Good luck
http://800notes.com/arts/Jb8EW-eDhQA/harassin ... ou-need-to-know
See Residents post here also:
http://800notes.com/forum/ta-34af6a034ba34b6/unending-collection-calls
Templates of Letters:
http://800notes.com/Phone.aspx/1-319-242-7350
To File complaints FDCPA/TCPA violations:
Your State Attorney General
Their State Attorney general
https://www.ftccomplaintassistant.gov/#&panel1-1
http://www.consumerfinance.gov/complaint/
Receivables Performance Management has been calling non-stop since April 23, 2014. Just like previous complaints, they call at all hours and never leave a message. I called their number to ask why the harassment. A female answered the phone and said, "You are being recorded, please verify your phone number." I told her she needed to give ME information about herself, who she works for, etc., before I was going to share any personal information. Of course she got upset and I hung up on her. My research of the number 424-646-3921 shows the number is located near West Manchester Blvd and South Fir Ave in Inglewood, CA