About 230-thousand SK Telecom customers got new SIM cards on Monday, the day the country’s biggest mobile carrier launched its free replacement service after a recent hacking incident.

In announcing the number, the carrier said two-point-63 million other customers had made online reservations for the service as of 6 p.m. Monday. 

SK Telecom is urging subscribers to sign up for the company’s SIM protection service to prevent hackers from accessing their personal information. 

As of 6 p.m. Monday, the number of subscribers registered for the SIM protection service had surged to seven-point-41 million. 

Altogether, ten million 270-thousand subscribers replaced their SIM cards or signed up for the SIM protection service.

That’s about 40 percent of SK Telecom’s 24 million subscribers and nearly two million budget phone users.