A friend runs a local business that relies on it's hard telephone lines to take orders.
They have recently been getting ddos-ed with robocalls for 20-30min periods and received an email with a ransom notice asking for BTC payment or that the calls will escalate.
They tried blocking a few of the numbers, but obviously the attackers are rotating lines regularly.
They can't only accept calls from a whitelist of callers as many customers are new.
Can you think of other solutions / services that can help out?