The call centre hire hundred of thousand employees to run such scams. It is a difficult task for the Indian police as the victims are located at overseas.
Thanks to an online vigilante Jim Browning, who hacked into the call center’s computer system and gain access to the CCTV camera. The CCTV camera capture clearly the conversation of the scammers and evidence have been obtained.
Source: https://www.bbc.com/news/technology-51740214