can't connect to a network abroad. Im told my sim card is not supported
Welcome to the community and thanks for posting. I'm sorry to hear you can't connect to a network abroad.
It doesn't necessarily mean your sim is not supported. You may not have roaming enabled on your account. We usually disable this as standard to make sure you don't get stung with charges.
You can now enable this via your online account. Here is a guide to follow:-
Online account > Plans and devices > Manage services > Enable roaming.
Or alternatively you can call 789 from the mobile or 0345 6000 789 from any other phone.
Hope this information helps.