Has anyone had success in switching their in car internet / wifi access from AT & T to T-MOBILE? I tried today with no success

 

You can't manually. The update of your vehicle's SIM card has to happen automatically via Over-The-Air update. Also, you can't have an active AT&T service, as it will prevent the update. Watch this video, it explains some stuff:

 

I did order the unit this guy is selling for wireless CarPlay/mirroring…I will give an update after I receive it.