(Telecompaper) Korean mobile operator LG Uplus and Japan's KDDI have claimed a commercial first in the world with the launch of their VoLTE roaming agreement. The VoLTE roaming services are available first for subscribers using LG Electronics' G Flex 2 smartphone in South Korea and Japan, the Korea Herald reports. LG Uplus said it plans to expand the service soon to other countries. With VoLTE, customers can make calls over the 4G network without losing their LTE data connection. In addition, VoLTE roaming services connect calls 20 times faster than through 3G roaming, the operator said. Japan's Docomo and Korean operator KT announced in February that they had conducted successful VoLTE roaming tests with US operator Verizon. Dutch operator KPN and China Mobile also started testing VoLTE roaming in late 2014, with plans to launch later this year.