While it is technically possible to block an incoming telephone number on our entire network, the result would be that they would be unable to reach any of their neighbors or family or businesses (that sandwich shop and thousands of other businesses) that use Sonic as their telephone carrier.
As a telecommunications common carrier, the FCC does not allow us to do that.
I would encourage you to engage with local law enforcement, and to consider a restraining order.
Reporting the harassment to the individual’s carrier may help, but I expect they’ll be similarly constrained, unless there is a court order that tells them to discontinue service.
All of that said, here is a potential easy solution: a phone and answering system that has a blocking feature. I’ve had good success with Panasonic DECT phones, and here is one with a one-button caller block feature: https://imgur.com/gallery/PEL3HTm
Panasonic KX-TGE433B Cordless Phone with Answering Machine- 3 Handsets https://www.amazon.com/dp/B01HXMJ14S/re ... MBbV2QVNMJ
I’m sorry I don’t have an easier fix!