If you have an EU/EEA mobile plan, roaming in Poland is generally free under "Roam Like at Home" rules. For UK and US plans, it's typically not free.
EU/EEA customers can usually use their domestic allowances for calls, texts, and data in Poland without extra charges. However, for UK travelers, many providers have reintroduced roaming fees since Brexit, so it's crucial to check your specific network's policy before you travel. US mobile plans almost always incur significant roaming charges in Poland unless you've purchased an international travel package from your carrier, which can still be quite costly.
To avoid unexpected bills, consider using an eSIM for your trip to Poland. An eSIM provides local data at affordable rates, connecting you to the strongest available major network, with the exact network varying by plan.