Block the number via My Verizon rather than via your phone. See "What is the most effective method for blocking spam calls?" at Blocks FAQs
Good answer, but I have pay for a subscription. I will look at ATT for better service.
You can block calls/messages from up to five phone numbers for free for up to 90 days in your My Verizon account. The numbers can be reentered/blocked after the 90 days are up.