What counts as the destination?
Use the exact countries on the itinerary and consider transit as well as the final stop. Ferries and aircraft may connect through services outside ordinary country lists. Your plan version or joining date can matter. Save the current official terms relevant to the trip rather than a general marketing page describing travel in broad terms.
Which activity could trigger a charge?
Ask about data, incoming and outgoing calls, SMS, voicemail and any daily access arrangement. A background sync can use data without an obvious foreground action. Switching off data roaming is not a complete answer for calls or other services. If a pass is available, identify when it begins, whether activation is required and what happens when its allowance or validity ends.
What if a second SIM handles data?
Select the intended data line and inspect automatic switching. The UK SIM can remain active for other purposes, with its own conditions. Check whether the phone supports the desired combination of active profiles. Keep an alternative way to authenticate important accounts if an SMS cannot arrive. A travel-data product does not automatically replace the functionality of the usual mobile number.
What should happen after returning?
Inspect the statement for the travel dates and any connecting journeys. Match disputed usage to the network and activity where possible. Keep relevant welcome messages and the conditions consulted before travel. Ask the provider to explain the particular item. A general description of an included destination cannot decide every charge on an individual account.
General practical explanation; confirm plan-specific rules with the provider.