If you have already made the recommended changes that Smarty publish for roaming, then it should work fine. The problem is that calls will not be included in your Smarty Plan.
If you look at the published Price Guide: https://cdn.smarty.co.uk/files/SMARTY-Price-Guide.pdf
on P18 you will see that Cape Verde is in band 3 for Roaming, so the charges for calls and data are eye-watering 😫.
If you can find a good wi-fi connection, you may be able to use an app like WhatsApp for communication without further charges.
