Deep Dive: How iOS Enables Overseas Wi-Fi Calling (WLoc, UDP 500/4500 & Transparent Gateway) Technical analysis of how iPhone registers Wi-Fi Calling via IMS/ePDG: WLoc network positioning, UDP 500/4500 IPsec NAT-T pass-through, and OpenClash / Mac Clash Verge transparent gateway setup. ⚡ Quick Answer (TL;DR Summary) Technical analysis of how iPhone registers Wi-Fi Calling via IMS/ePDG: WLoc network positioning, UDP 500/4500 IPsec NAT-T pass-through, and OpenClash / Mac Clash Verge transparent gateway setup. Guia de instalação passo a passo Scan the eSIM QR code on a stable Wi-Fi connection, or manually enter the SM-DP+ Address and Activation Code.Label your primary SIM and travel eSIM clearly to prevent accidental roaming data charges.Upon arrival at your destination, turn on Data Roaming on the travel eSIM and verify APN settings.If encountering no service or 3G only, toggle Airplane Mode or manually select an authorized roaming carrier network. Dicas essenciais e otimização Never delete the eSIM profile during travel; once deleted, the QR code cannot be scanned again.Disable "Allow Cellular Data Switching" to guarantee your primary carrier cannot incur roaming charges. 3. Step-by-Step Setup Tutorial Step 1: Go to Settings > Cellular > Primary SIM > Enable "Wi-Fi Calling on This iPhone".Step 2: Under Settings > Cellular > Cellular Data, select your Travel eSIM and toggle OFF "Allow Cellular Data Switching".Step 3: On your Primary SIM line, toggle OFF "Data Roaming" to prevent accidental carrier data charges.Step 4: If your primary SIM connects to an expensive local roaming partner, manually select an incompatible network in Network Selection to force the "No Service" trigger. 4. Critical Cost-Protection Advice To guarantee zero accidental billing, call your domestic carrier before flying to disable international roaming data while keeping Wi-Fi Calling active. Frequently Asked Questions (FAQ) Q: Can the same eSIM QR code be scanned and installed on multiple devices? A: No. Most travel eSIM profiles are single-use credentials. Once bound or deleted, they cannot be re-downloaded to another device. Q: How to use travel eSIM on devices without native eSIM support? A: You can use removable smart physical SIM adapters (such as ESTK, 5ber, or X-eSIM) to write and manage global eSIM profiles via their companion app. Q: Do Android devices support this feature? A: Yes, flagship devices including Google Pixel and Samsung Galaxy S23/S24 offer "Backup Calling" under SIM manager settings. Q: Why doesn’t the "Using Cellular Data" status appear? A: Verify: 1. Wi-Fi Calling is enabled on the primary line; 2. Primary line is not actively connected to a roaming tower; 3. Travel eSIM data is active. Related Guides & Keep-Alive Strategies 📖 Guia eSIM: Avoid High International Data Roaming Charges: Top 5 Traps 📖 Guia passo a passo para instalação e ativação segura de eSIM 📖 Guia eSIM: No Signal or Internet? 3-Step Emergency Troubleshoot Guide 📖 Guia eSIM: US Ultra Mobile PayGo eSIM Guide: Real T-Mobile Line at $3/Mo & Wi-Fi Calling Setup