Do you simply say, "I’m not interested in talking so please stop contacting me." ?

Or do you call up the clueless one and say, "Lets make this clear. I don’t want to be connected to you in whatever way—text, calls, emails, through common friends and acquaintances. I’m not responding to anything that you say or do coz I don’t care anymore."

Or do you just keep on ignoring and hope that this person gets a clue and hopefully the communications would eventually stop?

Right now I’m choosing the last one. - - - But believe me, it takes a lot of patience, especially if the person you’re trying to shoo away is totally clueless or just plain insensitive.