They've been calling me everyday, sometimes multiple times a day.

I called Verizon Wireless just now and they blocked the number for me.  It was very easy and only took a few minutes.  Verizon offers this service for free for up to 5 number.  You can increase the number of blocked numbers to 20 for 5 dollars per month.  But the first 5 are free.  

However, the block expires in 90 days.  Verizon sends a reminder a week before the expiration date.  You can call to renew an infinite number of times or simply set it up through your online account on their web site.

Very convenient and a good solution.

FWIW, my number has also been registered with the Do Not Call registry.  But obviously it didn't have an effect on these people.  I encourage Verizon customers to call and block the number.