“Your data is ready to be moved to new iPhone. This iCloud backup will be deleted in 7 days” message on my iPhone

D_Cash Said:

"There is a notification under settings that says 'Your data is ready to be moved to new iPhone. This iCloud backup will be deleted in 7 days'. I have plenty of room left in my iCloud, so it isn’t a storage issue. I did not get a new iPhone. There are no unknown devices listed under my Apple ID.[...]"

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Download All of iCloud Drive Prior:

To avoid losing your data, download all of iCloud to an external source. Use my User Tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip

I don't know what triggered it in your case, but it sounds like it might be related to this feature:

Get temporary iCloud storage when you buy a new iPhone or iPad - Apple Support

I can't say for certain – but it sounds like the thing that's going to get deleted in 7 days is some (temporary) backup of your phone's data, in iCloud. Not the data on the iPhone itself.