Sixfab confusion sixfab vs. commercial sim question

Hello. I’m trying to understand how sixfab manages to deliver a data connection without registering with the various commercial vendors of lte/4g, etc. It seems that this project provides a way to get a cellular data connection via the pi to users who need, for example, internet access. But I also read that a user can only register their sim with Sixfab; but Sixfab is not a telecom so please help me understand. Are there non-commercial 4g and lte networks that provide connectivity everywhere unbeknownst to us regular earthlings?

Thank you!