If you have upgraded to iOS 15 beta and now regretting it thankfully you can downgrade to iOS 14.
Step 1 Download the version of iOS firmware file from here.
Step 2: Start iTunes, head to the device’s.
Step 3: Now hold down the Option / Alt key on your Mac’s keyboard, or Shift key if you are on Windows, and click the Restore iPhone button.
Step 4: You will now be prompted to browse and select the IOS ipsw file you want to download, select the iOS 14 ipsw that you downloaded earlier.
Step 5: Select and open the file, which should begin the downgrading / restoring to iOS process.