ios 15

Good Point. Let me list the other requirements as well for the original poster.

Make sure that your iPhone is setup to meet the following requirements before you attempt to update the iOS version-

• Your iPhone must have a fast Wi-Fi connection; you cannot update over cellular data or a cellular hotspot
• The iPhone can not be in Low Power mode
• The battery state of charge must be above 50%
• Your iPhone must have at least 6GB or more free storage space
• Your iPhone cannot be connected through VPN
• You should leave the phone plugged in until it finishes updating, both to assure that it remains above 50% and to keep Wi-Fi enabled (Wi-Fi turns off when the phone sleeps if not connected to power).

Axel F.

That file, generally, gets deleted automatically. Try and Force ReStart your iPhone 7 Plus as shown below:

Force restart iPhone 7 Plus

Press and hold both the volume down button and the Sleep/Wake button at the same time. When the Apple logo appears, release both buttons. (DO NOT release Side Button when invited to Slide Power OFF). 

Axel F.

The iOS 15 update file that you saw previously was downloaded to your iPhone but NOT installed. You have that iOS 15 update file deleted. You do not have iOS 15 installed. You probably still have iOS 14. You can check by opening Settings ➔ General ➔ About ➔ Software Version.

The software update screen shot that you have posted is telling YOU that iOS 15 update is available for your iPhone. If you want to DOWNLOAD and INSTALL it then tap on Download and Install. If you do not want to install iOS 15 on your iPhone then leave things alone and do not download and install it.

Axel F.

How exactly are you attempting to Delete the update that you have already installed?

Axel F.

You also need to have at least a 50% charge on your battery to do the update. Plug your phone in and charge it or better yet, leave it plugged in during the update.