If you get the following error message in your cPanel/WHM

Sorry, the nameserver ip 12.34.56.78 cannot be removing since it is still registered with an ICANN register.

The cPanel/WHM query the IP addresses assigned to a hostname using whois system.

To stop the cPanel/WHM from query the a hotsname and its IP addresses, do the following:

1. Login to the WHM >> Main >> Tweak Settings
2. Check the checkbox next to: Disable whois lookups for the nameserver ip manager. to deactivate this feature/option
3. Scroll down the page and click the button "Save."