Technically, not impossible, but...
Public doesn't have any time of "share" plans or any type of offering that allows customers to have one number but 2 unique/different sim cards (think of one for a phone, but another for a smartwatch, etc.).
When I say technically not impossible, because Public Mobile doesn't allow 2 different sims to be active on the same account/same phone number, the way to do it would be to clone your sim card. Saying that, don't do this. I am not sure about the legality of cloning your sim card, but if you did and both happened to connect to the network at the same time, even for a split second, your service is going to get cancelled. Carriers would see this as someone stealing service and/or trying to pretend to be you.
So sorry, but if you want to going back and forth between different devices, you'll need to either pay for 2 plans or you'll have to keep moving your sim card from one device to the other.
