Possible ****ming and *******ion within MTN SA

On the 4th of March I was contact by an alleged employee from MTN. The person indicated that there is something wrong with my number and that he will send me an OTP to my number so that he can attend to the anomaly. It was evident that person had access to all my details prior to me sharing the OTP with him as he shared all my personal information with me. 5 minutes after the ended my airtime was gone. The person also put some kind of 'block' on my number so that I can't receive nor make any calls. I went to an MTN shop but they can't remove the block. It seems like the system is ******* and this definitely has an impact on the integrity of MTN and the manner in which they protect personal information of their clients.