Who called from 2136220000

I just looked up the phone number it is for a jewelry store in downtown Los Angeles. After I looked up the number this is the credentials that I was given.
Djm Jewelry
550 S Hill St Ste 920
Los Angeles, CA , 90013-2410  
Phone: 213-623-9080

I answered the call once, I couldn't understand anything that was said.  This was probably not in my best jugdement.  Since I have recieved the call on a regular basis for the past three days around 8 est.  As I type this they call again this time the caller ID reads 0.

sd

6:30 a.m. pst - google the number and it shows DJM Jewelers.  do a search through Big Yellow or 411 and it only comes up as a land line through Pacific Bell (which is now ATT).  There is no DJM Jewelers located in the building at 550 South Hill Street in Los Angeles.

I have received two calls from this number.  Each time I've answered I can hear an engine running but no one speaks.  Very strange.