Unable to delete iCloud backup

Hello prathameshW,

We have a great support article that might help with this. Please take a look at it here: View and manage iCloud device backups - Apple Support. Follow this guidance:

"View and manage iCloud backups on your iPhone, iPad, or iPod touch

1. On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud.
2. Do one of the following:

• iOS 16, iPadOS 16, or later: Tap iCloud Backup.
• iOS 15, iPadOS 15, or earlier: Tap Manage Storage, then tap Backups.

1. You see the devices with iCloud Backup turned on.
2. To delete a backup, tap the name of a device, then tap Delete & Turn Off Backup (or Delete Backup).

View and manage iCloud backups on your Mac

1. On your Mac, do one of the following:

• macOS Ventura: Choose Apple menu  > System Settings, click [your name] at the top of the sidebar, then click iCloud on the right.
• macOS 12 or earlier: Choose Apple menu  > System Preferences, click Apple ID, then click iCloud.

1. Click Manage, then click Backups. A list of devices that have iCloud Backup turned on is shown.
2. To delete a backup, select a device, then click Delete or ."

If those are the steps you are taking and the issue persists, further assistance may be needed. We want to make sure you reach the right team for help with your iPhone backup, so we recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here: Get Support - Apple.

Thank you for participating in the Apple Support Communities and have a wonderful day.