How to completely disable Flash SMS Messages

Government, Emergency and Enhanced Safety Alerts on iPhone - Apple Support (IN)

1. AMBER alerts and Public Safety Alerts aren’t available in all countries or regions.

2. Some government alerts can’t be turned off. Refer to your local government’s emergency alert policy to find out more.

If the messages really are from your provider, only they can stop them and you probably cannot block them.

Contact their call centre.