Can I also surf or call unlimited abroad?

You can. Up to 14 GB there are no additional costs for the EU.

Your usage within Belgium isn't included in this 14 GB: only what you use outside of Belgium is. If you use more, every MB used in the EU will be charged at € 0,004/MB. If you use over 20 GB during your bundle period, both within Belgium and abroad, you'll be able to continue surfing at a reduced speed of 512 kbps.

Outside the EU, the
normal roaming rates apply, and you can’t use your Unlimited data bundle.