I am trying to transfer files from my Iphone 12 to a new Iphone 15 using Icloud. It has been 24 hours
What can I do to either abort or speed up the process or is the phone just stuck on the transfer
iPhone 12, iOS 18
How are you trying to transfer it, from iCloud sync or iCloud backup? They are not the same thing. Did you follow this guidance→Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support
If you want to start over, first force restart the new iPhone→If your iPhone won't turn on or is frozen, then restart the old phone the same way.
Next, on the new iPhone go to Settings/General/Transfer or Reset iPhone/Erase All Content & Settings, followed by the transfer instructions in the link I posted above.