Who called from 2136291731

Constantly getting calls from 213 area code.  Please see if you can stop them.

I have received calls from this number, which I leave for my answer service to pick up, at the following times and dates:
May 25, 2012
7:19 am, 12:14 pm, 1:20 pm, 2:38 pm, 3:54 pm,
May 26, 2012
7:44 am, i:35 am
Interestingly no calls Sunday May 27
May 28
11:33 am, 12:27 pm, 12:42 pm, 2:44 pm, 3:46 pm, 5:16 pm, 5:21 pm
May 29
3:43 pm,
May 29
10:29 am, 11:01 am, 11:52, am 2:49 pm, 5:19 pm
May 31
7:24 am, 11:29 am, 12:01 am
June 1
7:24 am, 12:53 am
June 6
5:26 pm
June 7
9:16 am
It is now 10:53 am here.

still getting calls from "California, 213-629-1731  no one or message, please block.

Constantly calling - no one picks up

Who do you report these calls to?  What Agency is interested in detailing with these calls?

Is it not a Federal offence in both Canada and the USA.