Allowed Numbers in Family Allowances Not Working

I just switched my family from Verizon to T-Mobile.  One of my phones is an Android for my mother who is a dementia patient in assisted living. To keep her safe from scammers, Verizon had a family app that allowed me to restrict both incoming and outgoing calls and texts to a specific list of numbers that I set up in the app, what used to be called a "White List". If the number is on this list, the call was allowed to connect, if it's not on the list, it was blocked.

T-Mobile told me their Family Allowances service does the same thing, but I have not been able to make it work and, sadly, no one at T-Mobile Tech Support can figure it out either.  The Family Allowances Dashboard looks like the functionality is there, but obviously, there are serious flaws in the programing behind it that is preventing it from functioning as intended.

Has anyone out there been able to make Family Allowances work as I have described it? If not, are you aware of third party apps that work?