Like many others, we had a terrible time getting our iphone 12 pro activated.
TL;DR - turn off your wifi on phone, reboot, update os, call #832 to see if your test call goes through. Live chat agents are really awful, and the live chat system is super slow and clunky.
This is how I spent my Christmas -- unable to activate the iphone 12 pro.
The first agent took our IMEI and ICCID number and manually activated the phone. It deactivated right after we stopped the chat.
The second agent took our IMEI and ICCID number and manually activated the phone. It kept on the 'waiting for activation.' We sleuthed and tried turning off the wifi on the phone, rebooting, then updating the OS, then turning on the wifi again. It worked, but still had the waiting for activation message. This second agent ghosted us.
The 3rd agent listened to our issue, asked us to call #832, reported our issue, and told us that the waiting for activation message would go away in 24 hours. She had the decency to say goodbye and make sure we felt taken care of.