They're using computer synthesized voices now for two reasons: 1 – It's cheaper than using a real person (even at the pay rate they get in India, Pakistan, etc.), and 2 – The synthesized voice doesn't have a foreign accent to make people suspicious.
Oh, and a third reason: The computer can't testify in court should these scumbags ever be brought to trial. A human call center worker could tell all sorts of things about a criminal operation that wouldn't be saved on a hard disk.