My number *** was given to someone else

Yesterday I received 3 smses from Vodacom stating that a request has been made to them to do a sim swap or replacement on my sim card for possible theft or ***** and I was told to contact the Vodacom Customer Care number 082111. I called the customer care immediately and told them that I didn't request any sim swap or replacement on my sim card and they told me to go to a Vodacom shop within 3 hours because that's how long it would take for the number to be given to whoever made that request. I couldn't go to the shop because the nearest Vodacom shop is at least 100km from where I was at the time. My number is *** and yesterday later it was given to someone else. I need advice as to what to do because this is a case of theft.