POS INTERNATIONAL PURCHASE

I just want to know how you charge international online purchases?I obviously paid the company that i was purchasing from then got charged the exact same amount again.So i paid twice.This happens with netflix and Spotify as well.I've enquired about this and i was told that they will reverse or block the transaction.It is labelled as POS international transaction. Please clarify what this is...I was charged +-R940 twice.This is not the first time this happened.