******* Sim swap on mtn

Yesterday someone carried out a Sim swap on my sim card without my knowledge. Gained access to my banking apps and cleaned out my accounts. No one at mtn can tell me how this happened, just that it happens on a regular basis. Now this is an inconvenience to me as I have no money left, closed bank accounts. Which I still need to sort out. You cant speak to a consultant on 135 to put your Sim card on the watch list. I think this is the most pathetic service ever from mtn and iv been a loyal customer of theirs for years. If mtn knows they have a ***** issue, why are not doing anything about it.