[dragonwriter]

I suppose it's theoretically possible that a fraudulent caller had exploited your device or phone line in some way, though that's a rare and extreme case. Still, it doesn't hurt to mitigate it when you verify (of course, it's also theoretically possible the same attacker compromised your other phone, or just that of the business they are impersonating, too.)

[noodlesUK]

Especially with landlines it’s possible for them to stay on the line and pretend that they have hung up, play the dial tone and ring back noises, then continue the con. This is particularly easy with elderly people who have older phones.