Issued my Tablet MTN number to someone else

I Have been a client of MTN of over 15 years, I am really not happy with the service. My cell number has been given or RICA to someone else, without notifying me that if I do not make any phone calls from my tablet, then they will give it away. It is just not right even though I have been using it in my tablet. I do not make calls from the tablet and as such only browsed the Internet, send whatsapp and my little boy watch his stories. How can MTN just give my number to someone else without notifying me first. I feel this is invasion of my privacy and I demand my number back. AND I keep calling customer care and can't speak to "a Champion" as indicted by MTN voice. Keeps redirecting me back to the main menu. Really not happy at this stage.