Who are behind in blocking my Vodafone SIM card?

Today I talked to Vodafone Customer Care. They told me somebody called them to block my Vodafone SIM card giving my personal details. Who are those people who called Vodafone to block my Vodafone SIM card giving my personal details? However Vodafone advised me to replace the sim card. Today Vodafone store is closed. Tomorrow I'll go to Vodafone store to replace the sim card.