How to reduce spam calls with a traditional landline phone (not using AT&T digital home phone service)

Get a phone with a good call blocker, or a third-party blocking device. They work better than what the phone companies offer. No call blocker will work without having caller ID and you'd have to either use two blocking devices or get rid of the kitchen phone and replace it with a cordless handset from a cordless phone with call blocker. Cordless phones also won't work if the power goes out, you can always put a battery back up on them or digital service. 

Thanks so much for your input.  A follow up question or two, if I may.  Would this require subscribing to AT&T's Digital Home Phone service OR do you mean replacing the existing cordless phone base unit and handsets with a new unit (not sure what phone brand to look for so any suggestions would be appreciated) while still using the landline service (but adding in the CALLER ID service from AT&T).  Also, any suggestions on the third-party blocking devices and how does that work with the kitchen phone.. or doesn't?  Thanks so much!

Thank you very much for your information!  

I want to add one thing. If she really wants to keep the kitchen phone you could turn the ringer off on it so it wouldn't distract her while call blocking was doing it's thing. You'll have to look up on how to turn the ringer off. 

@rklang   Just an FYI:  Your mom is getting increased number of spam/anonymous calls because it’s Open Enrollment for Medicare which ends 12/7.  😔

This happens every year.  While spam calls are inevitable, it increases for those of us on Medicare.  I got close to 10 calls yesterday.  I let my machine pick them and they NEVER leave a message.   The number of calls should decrease in December.  🤪

@skeeterintexas While true it's still nice to make an allow list and let the robo calls go to press one to leave a message. 

Yes, more calls are definitely coming in because of the current Medicare enrollment period going on now. Unfortunately, she typically gets about 15 or more calls everyday during other times of the year - but these come from 'wanting to buy your house', life insurance, vehicle warranty expiration, Amazon, etc.  (I turned her ringer as far down as it goes on the old kitchen wall phone - from Ma Bell days!- but it doesn't seem to turn off - must be broken from age!?)  I do appreciate all the advice!  Now, I need to do some phone shopping-homework now.  :-)

If this is a 554 rotary dial wall phone or 500 desk phone, you have to take the cover off. There is a stop on the bell that needs to be bent so the ringer will turn completely off. If it's a touch tone phone than if a desk the same applies, wall phone was a bit different, but same principle. Wall 2554 desk 2500, this assumes it's a old Bell System phone. 

Does *77 call reject the spam and 3rd party calls?