I am so completely done with landline phones. The useless a-holes are relentless. In the trash with the landline. Blocking doesn't work, they just keep calling from other numbers. To hell with this stupid [***].
Listen to me. Login to your service provider site. Find the list of calls. Click (or right click depending on provider) and add the call to the block list. I have Verizon and this service is free. Block these MFs which is going to hurt them badly. You can, if you want, also buy a call blocker and block the whole area codes that you know no one calls you from there.