How does iPhone receive overseas SMS?

Mobile phone cards that don't open international roaming have no signal after going abroad, and they can't receive text messages and phone calls. Mobile phones that can roam internationally can be used abroad and at home. They can answer calls, make calls, receive short messages and send short messages. Generally, it is free to receive short messages when roaming internationally, but it costs money to send short messages. Different countries have different charging standards, so you can consult the local business hall.