No Caller ID harassment

I have received approximately 50 calls from a No Caller ID number that just hung up as soon as I answered. It was clearly an automated system that was making the calls and then finding no operators available when the call was answered by me, and hanging up. These calls happened throughout my mom's last days in a cancer hospice and during her funeral.

I finally got a human on the line today and the calls originated from Mobile Talk.

Does anybody know of any legislation or governing body where I can pursue harassment charges?