Name servers are more than just an A record. You need to create a name server record with Domain Registrar. Verifying name servers are not easy for many TLD, you have to trust your domain registrar. Only they can verify name server creation with Extensible Provisioning Protocol (EPP) commands.
Luckily for com/net/org domains, you can verify name server IP using
You can also use whois command to do the same.