***** sim card

I drove about 3km to buy a vodacom sim card from archamens store at orange farm few months back ,I was asked to bring my ID and a proof of residence. Because I didn't have those requried documents, I went back home and to fetch those documents.

But I have realized something strange from that sim card it is registered to someone else not me my question is why did they asked me to bring my documents ? The number is ***.