The federal government's position is "There is nothing we can do about it" even though most of the calls- if you play along- switch you to an America-based phone salesman working on commission. Almost all these folks work and live in Palm Beach County, FL, where boiler room phone scams are the biggest private employer (30,000 people the last time I heard). This has been going on for 30-40 years and started with timeshare and commodities options. The companies use standard credit card merchant accounts the government can quickly find and shut down. The local phone systems can be easily wiretapped. For the few big-wigs in India who are involved ("Hello, my name is Bobby") a few secret international arrest warrants that snag them on vacation in Europe will suffice. This is a huge illegal business, easily shut down. Why it isn't is a bit of a mystery to me.
So here is the thought experiment: Imagine if you picked up the phone tomorrow morning and heard that cheery female voice hidden behind two layers of Skype say "Hi, I'm from the Should We Legalize Presidential Assassinations? Project and we're doing a survey to gauge public support for Presidential assassinations and to see if you would like to make a small contribution to our campaign. To continue press one" . Note that "Presidential assassinations" can mean either assignations authorized by "A President"- (of what isn't specified) or assassinations aimed at a President. A bit ambiguous, but heck, no harm intended.
Exactly how many minutes do you think it will it take before the FBI gets a report, hits the "trace" button, finds the location and comes through the splintered doorway with guns drawn to take away everyone involved? Needless to say, no bail, multiple federal conspiracy charges each worth 20 years in jail on the way. My guess is 30 minutes unless the FBI decides to trace every cellphone call the perps have made in the past 10 years to see if anyone important is involved. Then it may take a few days. The claim that these operations can't be shut down is sheer silliness.
If Trump ever gets up in a debate with Hilary and said "I'll end these calls in the first 90 days of my Presidency" he'd be elected in a landslide. Hilary could do the same but she never does anything spontaneous.