MTN sim swap nightmare!

My MTN sim card was illegibly swapped twice this year alone, and on both occasions MTN says this was done around mid-night (~2300HRS). The first time this happened, the hackers accessed my Whatsapp account and sent out messages to my contacts asking them to e-wallet money to provided cell numbers. I subsequently submitted some of these hacker provided numbers to MTN with the hope that MTN would investigate this, but to my disappointment, I was told that they can't do anything about this. Surely for a large corporate such as MTN, they should have more secure systems that make it difficult for sim swaps to be effected so easily. One is left with a lot of questions, is this an inside job, who has access to my security passwords etc. Very disappointed!