Am I wrong to screen constant calls from my mother with dementia, who constantly complains?

So, in summary, Wondergirl, you are not wrong to screen your calls, and add any protective boundaries necessary for you to protect your sanity imo.
Even abandoning that phone altogether for answering your mother's calls. Anyone else can call on the new number.

Rainmom, I understand how you feel. My experience left me with phone issues, still. My privacy is very important to me, even more now.

Whenever dH is on the phone, I alert whenever I hear my name, or any sentence starting with "she". Crazy, I know. For his privacy rights, I try not to listen, go in another room with the t.v. on. Very soon, he comes in, talking-maybe to his mom-because 'they' want to involve me by proxy. Have learned to leave quickly.
If a call happens during my cooking dinner, I turn off the stove and leave.
It is that bad for me. Boundaries have been breached, and I am often left the only one still caring about an issue when they have continued on their merry ways, thinking I can solve it. Extreme boundaries, I call it.

When I had to CALL SCREEN for a different issue, but yes, unwanted calls, my doctor had to remind me that if I was there, listening, or playing the message later, it wasn't working for me, that the effect was the same as taking the call.
During that year, the phone company understood I had to change my number (a few times) and did not charge me. So, I changed the number.
Now, call forwarding would work also. As well as having a second number, a private cell phone for your use only-it never rings because you never give out tgat number.
Place the original number on silent, listen to messages only when you feel up to it, once a week?

The telephone became my enemy in my attempt at maintaining my sanity while looking after my mother. During one particularly bad period I counted 47 straight days when my phone rang - with it either being my mother or something having to do with my mother - and it seemed that every call came with some new problem or crisis. I tried to take a three day trip to the beach and told everyone not to call unless it was an emergency- that I needed a break... my mom called - twice, my brother called - twice, the social worker at moms rehab called. It got to the point, where like Pavlovs dog, I had a response - getting physically sick. I tried all sorts of strategy- assigned ringtones, cell number for some - landline for others, screened with caller ID, etc. I had a hard time just letting calls go to voicemail as it always got me obsessing about what bomb lay in wait for me. My moms calls were always the worst - either crying and laying on the guilt or raging and berating me. My mom passed three months ago and still when the phone rings I feel my stomach clench up. But yes - if you can do it, screen your calls. Sometimes you gotta do what you gotta do to hang on during this ride.

Wondergirl, do you already have caregivers in place? When my Dad had Agency caregivers the Caregiver would ask him who is he calling..... if the call was to me, the caregiver would ask if there was something she could do to help him. That usually worked unless Dad had a question only I could answer.

It also worked great when ever Dad got a call, the caregiver would stand nearby to overhear the call to make sure Dad wasn't giving out his social security number or a credit care number. If he was, she would halt the conversation, ask Dad who was he talking to, and if it didn't sound right, she would get on the phone.

I have an idea. Route those calls to the family members who think you should take all the calls. Problem solved, right?

What is your mother's living situation now? Does she have home care? If so, they will presumably call you or handle any real emergencies. If Mother is living alone then that in itself is the problem and needs to be addressed. If she is safe, you certainly should not be on-call 24/7.