Bone up your phone discipline and quit answering unknown calls from faked numbers. Quit worrying about who they are and what they are up to – assume they are up to no good and start blocking calls.
Criminals, Scammers and Fake Charities run by criminals break the laws and do not care about your rights. Most of the time, they can get away with it. In the case of the scammers run from India, Pakistan, Africa.... etc.... they almost certainly will get away with it.
Do NOT talk to the callers. They don't care if you are a day from Death's door, and are down to your last DIME. You tell them that, and they will call you tomorrow and take that dime if they can. And call back the day after to double check if you are dead.
Bad words do not impress them. Nor do threats, whistles or boat horns. Don't answer unknown calls, don't return calls to see who it was. Get serious about your phone discipline and get a call blocker and ask your phone carrier if they offer call blocking.