We were always being pestered by nuisance calls, so I bought a BT branded cordless phone (actually have 3 phones but you can get just the one). This incorporates call screening and blocking facilities without any extra ongoing costs and can be used with any service provider.
Have had it for a couple of years now and it has completely stopped nuisance calls.
You can programme friends, family etc in and they get through straight away. Any number not in the list gets a recorded message asking who is calling. A legitimate caller responds, the phone then rings and plays the callers message. You can choose to accept or reject the call, or leave it to let the answerphone switch in. Scammers and nuisance callers don’t respond and also silent calls don’t even cause the phone to ring.
Cant recommend it highly enough.
It incorporates Truecall technology, but there are no ongoing costs.
Stuart