Lorenzo Franceschi-Bicchierai published an interesting post on SIM hijacking highlighted the risks for end users and their exposure to this illegal practice. In 2017, hackers stole some personal information belonging to T-Mobile customers by exploiting a well-known vulnerability. It is possible to access certain customers data, including email addresses, billing account numbers, and the phones IMSI numbers. The attackers can use them to impersonate the target customer, crooks call the T-mobile customer care posing as the victim with the intent to trick the operator to issue a new SIM card.”]
Source: http://securityaffairs.co/wordpress/69279/hacking/sim-hijacking-t-mobile.html