🅰️ No. JB Voice SIM does not incur any additional data charges, whether you use it in Japan or overseas.

🗾 Use in Japan

📶 Mobile data service is available in Japan.
・You will receive high-speed data according to your subscribed plan（1GB–50GB）.
・After your high-speed data allowance is used up, your connection will not be disconnected. The speed will automatically be reduced to 200kbps, and you can continue using the internet.
💬 Examples:
LINE text messages, emails, and simple web browsing can still be used.

📢 Internet Settings in Japan
After arriving in Japan:
🍎 iPhone: You need to download the Configuration Profile.
🤖 Android: You need to configure the APN settings.

🌐 Overseas Roaming (Countries Outside Japan)

📞 Outside Japan, only the following services are available:
✅ Voice Calls and SMS
❌ Mobile data (internet access) is not available overseas.

Therefore:
・Whether mobile data is turned ON or OFF
・Whether you are connected to Wi-Fi or not

No international data roaming charges will occur.

📢 How to Use Overseas

After receiving the SIM card overseas:
Simply insert the SIM card into your smartphone to use voice calls and SMS.
❌ Do not download the Configuration Profile.
❌ Do not configure the APN settings.
This prevents your smartphone from attempting to establish mobile data communication.