1. GSMA,2017
2. Spam phone calls cost U.S. small businesses half-billion dollars in lost productivity,2014
3. U.S. Phones were hit by more than 50 billion robocalls in 2021,2023
4. FTC releases updated do not call registry data book; impersonator fraud tops list of consumer complaints;Jennifer,2023
5. Truecaller insights 2022 U.S. spam & scam report,2023