Also worth mentioning that although Virgin Mobile O2 haven't reintroduced EU roaming charges, as Virgin Mobile are a UK mobile provider, access to services in Spain is subject to the Roam Like Home policy you can find here - https://www.virginmedia.com/legal/services
This means that you are supposed to use your mobile in the UK more than abroad, otherwise you may be charged:
To be in line with our Roam Like Home Fair Use Policy your use must meet the following conditions:
2.1.1. In any rolling 4 month period, you must use more data, SMS and calls in the UK than the EU – we call this “prevailing domestic consumption”; or
2.1.2. In any rolling 4 month period, you must spend more days in the UK than the EU – we call this “prevailing domestic presence” (we count each day you connect to our network in the UK as a day in the UK).
4.If your use is outside of our Roam Like Home FUP we may apply a surcharge to the applicable domestic retail price while you are roaming in the EU. We will give you at least 2 weeks’ notice before applying any surcharge, and we will stop applying the surcharge as soon as your usage is in back in line with our Roam Like Home FUP. You can see the surcharge rates in our Tariff Table.
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I work for Virgin Media - but all opinions posted here are my own