You can't outsource your computer/cryptocurrency security to a 3rd party like your phone carrier. It's a recipe for disaster.
Hackers are targeting prominent bitcoiners
I completely agree with this. You can not trust all your apps blindly, it is a great risk to do that and sooner or later, you will regret it if you do keep sharing sensitive info with your mobile phone, even the words you type from your mobile phone are recording by your keyboard, how can you be sure they cannot reuse them for harmful reasons?
So try to be as secure as possible and only do it with PC, though it is also not that secure but at least it is way more than the so called smartphone.
As secure as possible with a pc would mean an isolated box, where your funds/keys are stored. Even if that means looking over then typing everything individually, better than a possibly compromised USB stick.