There are several ways to get them to stop calling, and I have been mostly successful over the decades. I'd like to share my latest method which has just about stopped my phone from ringing:
#1, and my latest victory: Answer the phone. Be friendly and agreeable, and stay on the line until you get leveled up to their sales closer. Then quickly explain that you wasting their time, politely, and hang up. Time is money for these jokers and you will get dropped off the shared lists in a heatbeat. It works!
#2 Mr Number or other call blocker apps. Very good for robocallers with spoofed numbers.
#3-ignore all unknown calls, but they -will- keep you on the active lists that they all share around, unless you do option one. They do -not- like their time wasted
#4- selectively block numbers. tedious and ineffective (see spoofing)
#5- Never give out your cell number except to family, get a landline and pay extra to only allow a select call list to get through. And get a junk ip phone number for any time you -must- put your number out into the public. My cousin does this and it works very well if you don't have time for option one.
(edit: avoid getting pissy with them or combative. I did that with one of the "windows tech teams" in india, blasted off at him with an eloquent stream of expletives (I was in a foul old-man mood), pissed off their manager, and got ip attacked/phone attacked for two days... but then they did go away... it actually stopped after I got one of them on the phone and apologized for being an asshole and called for a truce. It worked. They -are- people)
anyone else have any thoughts or tales of success or failure in fighting off these vultures?
Some days it's nice to be retired and have useless hobbies. This place being one of mine