These are scammers trying to sell you something like vacation and casinos vouchers in the indian reservation. They are hoping you pick up the phone, when you do not they leave no message and since this is a scam they block you from seeing who they are and no response if you call back. They call my home and cell phone on the average of several times a week. I am going to file a complaint, do not know if it will do any good though.
I'm so sick of ROBO calls. I received one from this number this morning, and the same company using a different number yesterday. Same area. I'm reporting to Do Not Call from now on.