5g home internet - phone not autoconnecting..

I recently switched to T-Mobile Home Internet, and neither mine (Pixel 4) or my daughter's (iPhone XS) automatically connect, upon returning home or restarting our phones. It's really not a major issue, until I forget to reconnect it, and use 2gigs of mobile data, when I only get 5 gigs of mobile data, per month to begin with. I'll try the wifi extender, that's a good idea.