Can't Block calls Verizon marks as spam

[etk2]

Ever since Verizon began marking some calls as spam, I cannot block one spam number. Perhaps this spammer has figured out a way to make the number unblockable and it's just a coincidence that it's marked by Verizon as spam. But perhaps the spam  designation is blocking a setting on the user side? 

I'm using a Panasonic cordless phone on copper wires. The spammer is from Newfoundland, New Jersey, and from what I've seen online I am not the only victim by far.