My number was potted and given to someone while I was told that I must go to cell C to unblock the number, what a shame cell c

My cell phone number was potted to Mtn while I was at home, I was using this number for many years and all of a sudden on Tuesday I received a message from cell C to say someone is trying to make a Sim swap I must call cell C, then I phone them they said they will block the number because I failed the security question, so to unlock it I must go to the nearest cell C, because it was already late, I decided to suspend my internet banking and everything else then in the morning I phoned cell C again and to my surprise I was told that my number is not a cell C number and it doesn't pick up on their systems, so I went to a cell C branch when I got there I was told that my number is now with Mtn, I mean how does that happen cell C I was promised that they have blocked it to unlock I must go to the cell C branch then boom my number is now an Mtn number and cell is is unable to help me, what a shock of my life I felt like I wanted to faint... Can someone please Try to help me in this regard I want my number back, as I hVe registered a lot of thing with it