Home Internet slow speed anyway to force b12?

^^^ Your issues are not going to go away anytime soon, so prepare and figure it will take about a year.
Some are lucky and dont have issues, but it will take TMobile a year or more to get every tower properly working. 

Been there, done that, Nokia tower, first few weeks around 100Mbps speeds but had to be reset every day, then 5 g died at my local tower, TMobile replaced my unit, still didnt work with 5 g, speeds were 8 to 30 mbps without 5g. Throttled down every evening, B12 band would switch to B2 and REALLY slow down. 

Went back to Spectrum, they met TMobile price of $49 but for one year only. Have a solid 117 Mbps service again and will try Tmobile again in Jan 2022 or sooner if they contacted me. I hate spectrum but Tmobile left me no choice.
You are kidding yourself if you think your issue is going to get fixed anytime soon. I worked on my issues for close to 6 weeks, I know the Nokia tower inside and out. Also for those who do not know, its not really all that hard to use another router with the Nokia Tower, just use the router that you want to use as an access point (another subject)

BTW, these are high quality Nokia Towers, the Wifi radio in them are as powerful as the most expensive routers on the market, the issue is, this is brand new technology and TMobile is still figuring out how to make it work with their brand new 5g network that is still being built, they will, sooner or later. As it does work for some right now.

Ps, No, you cant not “force B12” or any other band.