Is there a call blocker product or service for a telephone landline which will allow me to create a whitelist from the Contacts list on my iMac? (I do not want to enter the numbers manually, one-at-a-time.)
On my iPhone, I turned ON the "Silence Unknown Callers" in Settings. It is a great feature as it has stopped unwanted Spam calls from ringing thru on my iPhone.
I'd like to do the same thing with my Comcast landline. Thus, my question.
I'm not aware of Xfinity Voice home plans having whitelist as an option.
What I think you are looking for is Anonymous Call Rejection (ACR) as explained here:
Thanks for that suggestion but I've already tried ACR and it doesn't fix the problem. Spam calls still ring on my desktop.
I've also activated *77 and Nomorobo. Niether of them are effective spam blockers, either.
I believe Comcast could block these calls if they really wanted to, but they don't really want to.
Spammers have deep pocket$ and powerful lobbyists. Money talks.
I still seek a Whitelist solution for my Comcast landine.
Comcast home phone service works with standard POTS devices. Amazon has some devices for around $100 that claim to apply whitelisting and auto-hangup on all other calls. I have never used any of them and can't give a good recommendation of which one to get.
As to being able to effectively block calls, there is several scammers taking advantage of that the caller id system is historically not authenticated. This means there is a number of voice over IP services that just blindly take the customer's claimed phone number as being legitimate.
A solution to this problem is called STIR/SHAKEN. Comcast and AT&T were the first major telephone service provides to claim support for the new standard. However, the FCC decided to set a June 30, 2021 date to make it mandatory for all providers. Until that date, we will continue to have scammers that seek out providers that allow transmitting an arbitrary caller id. Discussions of setting a deadline go back to 2019, why the FCC didn't establish a requirement soon is beyond me.
As to if Comcast could be providing whitelisting, I agree technically they could. My best guess is they decided this could lead to consumer confusion. For example, I have had to try multiple times to explain to Comcast support techs that "Call Forwarding" and "Advanced Call Forwarding" are not the same thing. Some have even ask if we tried standard Call Fordward instead which seems to strongly indicate that even Comcast's own support employees don't understand how similar name things for their service function very differently.
If you need to have whitelisting from the phone service provider directly instead of using a POTS device to accomplish it, you may unfortantly need to shop around for a different provider.