How can a country like the US allow its phone system to be taken over by criminals? How robocalls became America's most prevalent crime Two inventions are behind the robocall scourge. Voice over Internet Protocol (VoIP) dialing — the technology used by apps like Skype — lets scammers place millions of calls a day, costing just $0.006 per minute if a call is answered. The other breakthrough is "neighborhood spoofing," which disguises robocalls to appear on caller ID with the same area code as the number being dialed, instead of an 800 number or distant area code. By one estimate, 90 percent of scam calls from abroad now show up as U.S. numbers.