Unplug the iPhone from the Mac
Open Finder on the Mac
Select your iPhone in the Finder sidebar
Click Eject next to the iPhone name
Open Photos on the Mac
Go to the Import tab
Click the eject icon next to the iPhone
Open Music on the Mac
Select the iPhone in the sidebar
Click the eject icon
Open Apple Devices or iTunes
Select the iPhone
Click the eject icon
Turn off Bluetooth on the Mac
Turn off Wi-Fi on the Mac
Disable Handoff on the Mac
Sign out of iCloud on the Mac if needed
Remove the iPhone from trusted devices in Apple ID settings if needed