If we pick-up but say nothing, they end the call immediately.
If we pick-up and speak, it activates their pre-recorded message.
Now, we just refuse to answer at all - as soon as the answer-phone starts ("Please leave a message after the tone"), they end their call.
It's still annoying...
Getting 4-6 cold calls per day on (otherwise rarely used) landline - sometimes before 8.00 on a Saturday morning, and sometimes 2 calls in 5 minutes.
All are pre-recorded messages (usually with an American accent) purporting to be from Amazon Prime, BT Broadband ("Your internet service is about...