Talk:Korea (South)/@comment-202.152.87.222-20170221031002/@comment-28786381-20170221050918

Generally speaking (and for KT/olleh only), the standard rental SIMs only have 2 options: data-only (don't need to return the SIM) and data+voice+text (must return the SIM). Providers like EG SIM have a voice+text prepaid balance, and data is only offered in 1-month packages. Olleh's regular SIM plan works similarly, but they allow you to use your prepaid balance for data (at a terrible rate)

As for international calls, I don't really have any real advice. If you're savvy enough to research SIMs on this site, then you're probably savvy enough to figure out that it's most effective to have some kind of VoIP service that you can use from wherever you have data.