(Telecompaper) Korean operator SK Telecom announced the milestone of over 1 million subscribers for its joyn services, just 50 days after launching the messaging service. The GSMA, which has worked with global operators to develop the joyn brand and services, said that SK Telecom's success should encourage other operators to adopt joyn. SK has steadily added to its service, most recently in late January giving its smartphone customers on flat-rate plans unlimited joyn SMS/IMS services. Data fees incurred from sending/receiving messages over the service are not deducted from subscribers' data allowances. In future joyn will be integrated with the VoLTE service, supporting HD Voice. This will allow customers to send videos and files during a LTE voice call. Furthermore, SK Telecom plans to open up the joyn APIs to developers to launch services such as games, SNS and mobile commerce.