How to avoid and prevent SIM Card swapping

How to avoid and prevent SIM Card swapping

My friend got his mobile number stolen essentially and is being used by someone else to get into his accounts(bank, credit cards, apple pay, etc.)

Almost certain his mobile provider's support was social engineered into thinking it was him requesting a phone number transfer

HOW DO WE PREPARE AGAINST THIS?? We can't stop social engineering, so what do we do for future?

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