How to change my name server to other then Cloudflare's? Domain registrar

I have my domains registered at Cloudflare.

Domain Registration

Registrar:

Cloudflare

I want to change my DNS away from rob.ns.cloudflare.com & sara.ns.cloudflare.com to a custom name server such as ns1.test.com & ns2.test.com.

Is this possible with CloudFlare? Again my domains are registered here.

Generally you cant change your nameservers. The only exception is if you want to use records of your own domain as nameservers, in which case you could use custom nameservers (https://support.cloudflare.com/hc/en-us/articles/200169006-Can-I-get-vanity-or-custom-NameServers-using-Cloudflare-) but this will require at least a Business plan.