I screen all my landline calls.  They're calling me about 6-8 times a day.  Really persistent.

This number calls my office every hour since last Thursday ( Jan 28th)!  When I am back at work in the morning there will be 6-7 voice messages with just a hung-up sound recorded. When I pickup the phone none says anything and disconnects. I tried to call back: "The Number is not in service" -auto message. I guess it's better to block this caller if possible

Called twice. Left no messages.