I'm going to move to Poznan from Berlin using DB train. However, the arrival time is 19:27, and I must purchase and activate SIM card immediately in order to get to my AirBnB room.
According to Prepaid data SIM card wiki on Poland, I can purchase a SIM card anywhere but the registration must be done from July 2016, which must be in "the stores and sales outlets of the providers".
It's not possible anymore to buy a prepaid starter set without showing your ID. Take care, that some places like kiosks still sell them, but you can't register there. But without registration, you SIM card won't be activated. That's why it's recommended to go directly to an operator's store instead located in towns and shopping centers.
But I wonder if these shops are still open around 20:00. Is it possible to buy a SIM card and activate it after I arrive at Poznan Glowny station at 19:27? Or is there any other way to get a mobile network?