My Mom's MTN number given to someone else

Shocked, sad and disappointed. Cannot believe this, is like I'm dreaming. My Mom has been using *** over a decade. She is running a guest house business in Welkom in the Free State province. 2 months ago her number was not working and when she followed it up, it was given to another white guy in Joburg. Don't know how cos that number is rica'red under her name. Business has been down ever since as no longer calls coming in for bookings. Anyone who can help please contact her on ***