Vodacom gives out your number???

I received a brand new contact with sim card less than a week ago, I have already had few people and companies calling. How is it that they have my number within a week and I am not even using the sim??????? So I contacted Vodacom and the agent told me its someones else old number and they can give me a new one for R161 and I cant even do a sim swap. Now I as the consumer have to deal with all these marketing calls FOR TWO YEARS AND THEY DON'T EVEN CARE. Absolutely unacceptable, made a mistake going back to Vodacom!