I currently have no service in Serbia. Roaming is switched on, even though I only want to text.
Welcome to the Community
Sorry to hear about the issues you're having with the roaming service.
As well as being activated on your handset, can you confirm you've got the roaming provisioned on your online account?
Just head to 'Plan and device' and then 'Manage services'.
Let me know how you get on.
Mark YForum Team