Personally, I leave it to my answer phone to answer it. If it sounds like something legit. I can pick up and interrupt but I've found that 99% of the time they don't even try and leave a message, they just hang up. Anybody legimate would, of course, leave a message. The exception seems to be the computer generated scam messages...& they are usually transparent enough but also fairly rare.
The BT phones intercept calls with a prompt for the caller to announce themselves. Only once they’ve done this will unknown callers be put through, where you still have the option to send them to voicemail. Because the scam calls are auto-dialled, they’ll almost never do this as they know it’s a dead end.
Simply blocking a non-existent number that constantly changes is pointless.
You do not need the Choose To Refuse service, and in fact, I do not think its sold any more.
All the phone needs is a working caller display service, which you already have if you can see the number called.
You will need to add the phone numbers that you always want to receive calls from, into the BT4600 phone directory, and enable BT Call Guardian on the phone.
The preferred option is "announce", for all other calls. You can always add any new person that has to announce themselves, to the phone directory.
Just checked and it's still in my package at £0.00 per month. Seems like something ineffective but likely to tie you to BT instead of another provider. Have ordered a BT 4600 in the hope it will be more effective than my current landline.
I'm hoping someone will invent a phone which sends a powerful electric shock through to any scam caller. One day.
Cheers.