Who called from 2136707461

This number 213-670-7461 call and I hear no one on the other in. They call from Los Angeles,California. I call that number ask them not to call again and some other words. I also say I am on Do Not Call list from FTC. Then I press my blacklistbutton on the Pre Call Brocker.

they do the same- and call early morning and late at night

This # calls a dozen times a day and no one is on the line. How do I get it to stop?