I answered a phone call on my work phone 1 time it was a sales/scam phone call - I told them not to call me at work again. Now, they call my work phone at least 5 times a day (I do not answer) but they do not leave a message.
Number is an XO Communications number. Call them (XO), and complain, that they are serving a criminal enterprise, and demand that they stop providing service. One of their numbers is (858) 244-4000 - West Coast. Another is (703) 547-2000 - East Coast. Report XO Communications to the FCC, and to your State Attorney Generals Office.