Complaints about Phone Numbers876-890-####

Person calling from this # told my grandma she won a sweepstakes. Has gotten thousands out of her scamming her

Called saying they lost money then threatened my life

Told the recipient that he won 8.5 Million dollars.

We keep receiving call from this telephone no. Last month it showed on our bill, I explained to our carrier that we did not know any one related to this no. We are seniors and what can we do to stop these calls? The caller states he is from sweepstakes.