MTN DONT CARE-BEWARE

I had a Mobile number until a couple months ago .. I’d had it for about 20 years or more and suddenly I saw somebody’s photo, other than myself, against my phone number I attempted to contact MTN after 13 tries and no help/replies I got a message to say it was no longer my number .. I was away abroad I knew nothing about all this the same day I tried to get my old number back I got no assistance they WERE NOT INTERESTED.. it’s my business number I offered to pay for the person who now has my number to get set up with another number etc BUT THEY WERE NOT INTERESTED this happened approximately mid October I still want my old number anything I can do??