I would think that an online-only MVNO like Ting.com would be harder to fool - even if their call agent fell for the trick, they'd still have to mail a new sim

I would think that an online-only MVNO like Ting.com would be harder to fool - even if their call agent fell for the trick, they'd still have to mail a new sim out. But you'd have to log in yourself to swap the sim using the Ting website. As I understand it, attacker would have to fool you and coax you to swap the sim.