Earlier this year, Nguyen Thi Ha Thu in Ho Chi Minh City lost VND2.1 billion ($84,427) after an individual, who claimed to be a MobiFone employee, called and asked if she wanted to upgrade her SIM.
The caller provided Ha with a code and told her to send it to a MobiFone number that starts with 901, which is also one of the network operator’s number.
"The caller read out all my personal information so I had no doubt."
Several hours after sending the code to the given number, her SIM was locked, and her VND2.1 billion savings disappeared.
Thanh Tam in HCMC was similarly scammed and lost VND30 million in 30 minutes.
After disabling her SIM card, the caller changed her bank app password and was able to access it to transfer the money to other accounts.
The Vietnam Competition and Consumer Authority (VCCA) has confirmed that it has received many reports of this type of scam recently.
The caller typically tries to get the SIM details of a victim and activate it as an electronic SIM on another device. This person then calls the victim’s bank, gives the required personal ID and requests a new internet banking password.
Several banks including HSBC, VPBank and NamABank have been repeatedly warning its customers about this scam.
"This type of scam was reported a few years ago but is now resurfacing as many people are looking to upgrade their SIM to 4G or 5G," VPBank said.
Several banks have tightened their verification process to prevent this scam, using voice or face recognition technology. Some lenders are blocking transactions of an account for 12 hours after its password is changed to prevent stealing.