Also countries like Tunisia and Turkey are not in the EU so there are no capped protections on roaming charges. Those capped charges only apply to countries within the EU.
This is how not to get caught out:-
The cost of data can really be a killer if you're travelling beyond Europe. says all mobile operators have to cut off your data connection once you have used around £40 to £50 of data per month, wherever you travel in the world, unless you choose another limit. The precise figure varies from company to company. The provider must send you an alert when you reach 80% and then 100% of the agreed data roaming limit, and must stop the data at the 100% point, unless you agree to continue to use data.
Other than leaving your phone/tablet at home, the best way to avoid running up an unexpected bill is to switch off data roaming before you leave the UK. That will ensure your device isn't racking up costs without you realising it (many phones and tablets are programmed to automatically seek out mobile connections and use them to update apps even when you're not actively using the device).
If you want/need to access the web, use free Wi-Fi in places such as hotels, cafes and restaurants whenever you can – though avoid making online purchases or accessing your bank account via such services. You don't need data roaming switched on to access Wi-Fi. However, make sure you are, indeed, connecting to the correct network and not an "evil twin," which is a lookalike connection designed to trick you, says security firm Norton.
Make sure you download what you need before you leave home, including apps, books, films or music, plus city maps, guides, etc, says Ofcom, and check downloads are fully completed before you leave.
If you want to use your mobile phone abroad, but don't fancy the roaming charges, one way to potentially cut your costs is to buy a sim card – either a local one that you purchase when you get to your destination, or a global/international one that can typically be bought in advance from a specialist provider. When buying, make sure your phone is "unlocked" and that it's compatible with your destination country's radio frequency.
Buying a local pay-as-you-go sim means that you'll be using a different number, but will ensure you pay local prices and can be particularly worthwhile for those who frequently visit the same country.
Beware accidental roaming. This is where you're visiting an area close to another country and your phone picks up the network across the border. If this happens, you may be charged as though you were roaming in that other country, so take care and keep a close eye on your phone.