It's possible, but this method typically requires you to share private information to verify the caller's identity. If you've been sloppy with your privacy, gotten phished, etc., you could be vulnerable to this. Additionally, there have been instances where hackers have people on the inside of the telecommunications company helping them pull off the attack.

So yeah, you should not be relying on SMS authentication to protect significant amounts (I mean, it's still better than no other protection at all), regardless of carrier.