iPhone 7 stuck in '1 minute left' screen during data transfer to iPhone 12

"There is 1 min left for data transfer."

I've seen a lot of these posts with varying answers. Most of them are from a while ago. This whole process makes me want to return my phone. I'm trying to transfer my iPhone 7 to a 12.

The 7 won't even let me cancel the transfer. The 12 looks like it's done with the data transfer and is now asking if I want to transfer my phone # from my carrier. When I say yes, nothing happens. I don't know what to do... Any suggestions besides waiting 12 hours & hoping it fixes itself?

[Re-Titled by Moderator]