I used to work on toll fraud as part of IT for a large tech organization. Not FAANG but several thousand employees.

My impression at the time was the fraud detection heuristics helped, but the root cause was scammers working with telcos overseas. Many of these companies have extremely high rates in the first place, and turn a blind eye to the practice because it makes them much of their money.

Some VoIP providers like Twilio may be the same. As a middleman / carrier, they will always profit from traffic on their network, even if they disavow it as fraudulent and wag their finger at you about it.