STRANGERS DOING SIM SWAP

On the 20th Dec someone did a SIM Swap on my number and that time I was driving the phone just lost network but the time I realize that network is not coming back I went to the mall to check, and they confirmed that Sim Swap was done on my number. How can MTN allow that without sending message to confirm if am doing SIM Swap or not because of their incompetence I was hacked my money was ****** in the bank.