I'm surprised myself to say this - Xfinity Mobile had the best security of all the mobile phone providers. SIM Swap is via a generated code that you have to login to generate. Customer Service verifies a ton of information before they look into your account. It's also generally cheaper than TMobile - but some features are sorely missing/lacking - they're still new.

All that said, Comcast Internet's business practices is outright awful - they lied to me multiple times about my plan and discounts. And you need Comcast to use Xfinity - it's very expensive otherwise.