In your domain registrars control panel you should look for an option to set/change the NS (Name server) records for the domain.
A common mistake we see is users setting “NS” records in their own domains DNS records. This is wrong.
The records that actually need to be changed are held in the records of the parent domain TLD (Top Level Domain) which is the .com or .net part of your domain (Sometimes called the domain extension).
By changing the NS in the TLD you are reassigning the authority of your domain to other DNS servers. So you can see that changing the NS records in your own domains DNS will not work and is pointless anyway since you are attempting to change the DNS servers used by the domain so these records will be ignored.
On most domain registrars websites, the page for setting "name server" records of your domain will be separate from the page for setting DNS records of the domain. Sometimes you may even have to request the change through a support ticket with that domain registrar.
Please contact your domain registrar if you are still having problems.
