I called a Korean friend and was told that it was an empty number because there was no international roaming, but I received his short message today. What the hell is going on?

International roaming refers to the function of making and receiving calls when roaming abroad. If you make a foreign call in your own country, you don't need to open the international roaming function.

This function you are talking about is called international long-distance or international long-term rights service, which refers to the function of making foreign calls with domestic numbers or sending short messages with foreign phones.

But you don't need to open an international long-distance service to answer foreign calls or receive foreign short messages.

I don't know. Can you understand what I said? I hope I can help you.