It's probably a little more complicated than buying a phone and sim card then just buying credit for it.
What's so complicated? You go to the shop, buy the phone, then buy a sim card from any supermarket and voila. Nothing difficult there. Or if you buy it from the operator, it will come with a sim card included.
If not, I'm all ears because I really want to do this.
Okay, it's simple.
Go to the Play shop. Buy a phone "na karta" - it will come with a sim card. You put the sim card in the phone, and voila. You're off. You can add money to it in lots of places.
Also, I want to understand exactly what I'm paying for and how much of the service I'm getting.
Then use their website before you go. Play is pretty straightfoward though.
You're not gonna survive in Poland if you need your hand held like this...