1. Run the Flashing Script  
Run the Regional_Flasher.bat file.  
- The script will flash a few images and then reboot to fastbootd.  
- Wait for your phone to boot into fastbootd. When it does, select English on your phone to proceed with the flashing script.  
- The script will then flash the remaining images.  

2. Do you want to wipe?  
You will be asked if you want to wipe data:  
- If YES, you will be instructed to wipe data manually in fastbootd. After the wipe, the phone will boot into OxygenOS.  
- If NO, the phone will simply reboot into OxygenOS without wiping.  

3. Fix Signal Issues (If Needed)  
If your OnePlus 13 loses network connectivity after flashing/changing region, install the appropriate "signal fix module" using kernelsu/magisk:  
- EU/GLO models running non-EU/GLO firmware → Flash fix-signal-oneplus13euglo.zip  
- India models running non-India firmware → Flash fix-signal-oneplus13IN.zip  
- China (CN) models running non-CN firmware → Flash fix-signal-oneplus13-v3.zip  
- After flashing, reboot your device, and the signal should be restored.