I spent an hour on Apple Support. The reason for most of the wireless charging issues is that the older wireless chargers
are 10 watt chargers. Apple recommends at least 20 Watts for an I phone 12. The wireless charger that worked on my I phone 8 is 10watts and will not work. I found a 36 watt wireless charger from Otter Box , purchased through Apple, for $54.95
In addition, I could not get my speaker phone to work on incoming calls. That is because my Cell carrier still had my
4 G service on. I had to call them to activate 5 G for an I phone 12. You can go to settings/Cellular Data/Cellular Data Options
Roaming ON, select LTE. This basically turns your phone bac into a 4 G phone. Your speaker phone phone will then work
until you are reset to 5G. Just don't forget to set it back to 5G after contacting your carrier