Roaming is using your home SIM on a foreign network. Whether it is free or expensive depends entirely on where you are and your plan.
Inside your home region
Within the EU/EEA, “roam like at home” rules mean most European plans work abroad at no extra cost, within a fair-use limit. Several operators run similar zones elsewhere.
Outside it
Beyond your included zone, calls, texts and especially data can be billed per minute or per megabyte at rates far above home prices. Data is the usual culprit, because apps keep refreshing in the background.
Three settings that protect you
Before you land: turn off data roaming unless you know it is included; enable your operator’s spending cap or travel pass; and disable background app refresh. If in doubt, a local SIM or eSIM is often cheaper than paying per megabyte.



