Thanks for your post on the Community Forum and welcome. I'm sorry that you're having a problem with your data roaming service. If you are a new customer, please see the following details here: Before You Go.
Please verify that your data roaming setting on your mobile is enabled and that your APN settings are correct as noted on this post: Roaming - FAQs or you can find your handset on our following website to have the configuration settings for mobile internet sent to your phone: Online Send Phone Settings. If your handset isn’t on this list, you will need to manually reset the APN settings.
Also have a look at the following online Help & Support Page: Roaming Hub if you have access to WiFi.
If you are still having an issue with this, please send me a private message by clicking this link: PM me here and send the following details: