I've been looking at this lately as I setup new phone service for my MIL who's moving to a place with unreliable power. Some phone companies have whitelist services, although if your telco is like CenturyLink of Washington state, they don't appear to want to actually be in the phone business anymore and all the useful services are grandfathered, ordering a phone line is an ordeal and pricing is crazy (OTOH, the line quality seems to be good if you can get it). If you've got a voip line, you've got way more options though; I think most providers should give you options to whitelist.
Assuming your telco won't help you with whitelisting, your options are maybe? getting a new cordless system with caller id whitelisting, it seems like maybe some of the newest panasonic dect systems can do it (that will take care of the answering machine needs as well). Or getting an external box, most likely inline with your phone.
I don't have either yet, but it seems like reasonable options include the Digitone proseries II [1], or the Sentry call blocker[2]. Both are more expensive than they should be (IMHO), but offer some amount of whitelisting and blacklisting. The Digitone has a longer history in the industry, and what looks like a clumsier interface; the Sentry has a good, but slightly messy feature for handling inbound calls from numbers that aren't 'known', for those calls, it answers and plays an outgoing greeting (customizable in the 3.x device, prerecorded in 2.x), if the caller presses 0, their number is added to the white list and they can call back; from reviews, I gather on the 2.x series pressing 0 add you to the whitelist and then hangs up on you; on the 3.x series, pressing 0 generates a fake ringback, makes the device ring (but not phones on the line) and after 9 fake rings will let the caller leave a message on the sentry device (2 message capacity, FIFO). This is like not quite right; the recommendation from reviewers is to record a message asking people to press 0 and then hangup and call back, rather than having them go through the weird ringing stuff. There's some negative comments about recording quality.
I've tried both of these devices. The Digitone (and anything similar) is useless, as it requires you to press a button every time you receive a call from a "bad" number. I did this for about a week, logging hundreds of incoming calls, and I rarely saw a duplicated number. So you'll just be pressing the button all the time - might as well just pick up the phone and hang up.
The Sentry is much better, but has some notable flaws.
The Sentry works as a whitelist, so it blocks all calls by default. After you enter your whitelist (family, friends, etc.), you'll get three types of calls:
-Good Calls: From people on your approved list. These calls ring through as normal.
-Bad Calls: From idiots (aka robocalls). The idiots aren't smart enough to press a button, so they don't, and then the Sentry hangs up the call.
-Other Calls: From humans who are (ideally) not idiots, but aren't (yet) on your list.
This third item is where the Sentry really needs improvement. Other callers hear a (horrible quality) outgoing message, so they can either hang up, or press a key to leave a message - on the Sentry, not your answering machine/voicemail. The message they leave is only 20 seconds, and you can only receive two messages. And you can't screen these calls - you don't actually hear the person leaving the message, and you can't pick up the call if it turns out it's valid. And the Sentry doesn't timestamp the message. There's a log of calls, but you have to work to figure out who actually called, especially if the caller's message was cut off.
(What I would prefer is to have callers press a button, then my phone rings like normal.)
If you don't get a lot of "new" numbers calling you, the Sentry isn't bad. But you will miss some calls, especially at first. Thankfully, there's an on/off toggle for those times when you're expecting an important call from an unknown number (delivery guy, hospital).
Please email me a review if you set one up. I'm currently waiting for the welcome packet so I can try the CenturyLink options, but I'm not holding my breath and will need to get something soon, cause junky calls are already coming in. (surprising noone)
Assuming your telco won't help you with whitelisting, your options are maybe? getting a new cordless system with caller id whitelisting, it seems like maybe some of the newest panasonic dect systems can do it (that will take care of the answering machine needs as well). Or getting an external box, most likely inline with your phone.
I don't have either yet, but it seems like reasonable options include the Digitone proseries II [1], or the Sentry call blocker[2]. Both are more expensive than they should be (IMHO), but offer some amount of whitelisting and blacklisting. The Digitone has a longer history in the industry, and what looks like a clumsier interface; the Sentry has a good, but slightly messy feature for handling inbound calls from numbers that aren't 'known', for those calls, it answers and plays an outgoing greeting (customizable in the 3.x device, prerecorded in 2.x), if the caller presses 0, their number is added to the white list and they can call back; from reviews, I gather on the 2.x series pressing 0 add you to the whitelist and then hangs up on you; on the 3.x series, pressing 0 generates a fake ringback, makes the device ring (but not phones on the line) and after 9 fake rings will let the caller leave a message on the sentry device (2 message capacity, FIFO). This is like not quite right; the recommendation from reviewers is to record a message asking people to press 0 and then hangup and call back, rather than having them go through the weird ringing stuff. There's some negative comments about recording quality.
[1] https://digitone.com/ [2] https://www.telsentry.com/