International roaming on prepaid plan

I’m trying to set up international roaming on a prepaid plan after I’m already in Europe. The help system says: 

1. Log in to your Self Serve account.
2. In the drop-down menu, select Mobile services.
3. Select manage beside the Add-ons section.
4. Find International Voice Roaming ($0/month) and select Add to Plan so you can call and text while travelling outside of Canada and the U.S.

and so on. 

This help information seems to be outdated as the menu options don’t include “Mobile services” and when I go to adding add-ons, there is no international option listed. The information for the US roaming implies that it works internationally but I tried it and have had no luck. Is international roaming actually possible on a prepaid plan, and if so, how?

Thanks!