The following applies to Directnic namservers
Login to Directnic
Go to the Domain Manager
Click on the DNS icon for the website
That takes you to Modify Nameservers
Near the center of the screen is a link that states
You must have a minimum of two nameservers for any domain.
Click on Create nameserver
That takes you to Namesaver creation and the two existing nameserver names and IP addresses
Host Record/Nameserver IP Address Delete Nameserver Modify Nameserver
NS1.SCASP.COM 220.127.116.11 Delete Modify
NS2.SCASP.COM 18.104.22.168 Delete Modify
To change the IP address you need to click on modify for each name server, and insert the new IP address in the appropriate block, you can only do one at a time.
The formatting on this may not hold, but it gives you an idea how to do it.