Just received a call from this number. It rang 2 times then they hung up. Immediately after they hung up I received a text from Verizon stating they received returned mail sent to me and to log on to their website and update my address.
It was legitimate. I recently moved and had not updated Verizon with my new mailing address.
Making sure you don't answer in any way is a good place to start is free. A call blocker may be of some help for a landline and a blocking app for a cell. You have to be patient and give it time, but after enough calls and getting nothing from your number, they get tired of it and eventually quit. Stopping all junk calls probably isn't possible, but you can definitely cut back on them the way stated. Ignoring unknown callers may be the easiest and best defense. If they know you often answer the phone, they'll keep calling. They gain nothing from numbers with no kind of answer.