No registrar for domains, email notification upon updating name servers

[ibad]

I am selling ccTlds, currently, there is neither an API available to configure auto registration nor any registrar provide those cctlds for registration and managing with a whmcs module, as a result, i am to manually register them once i receive an order from client and later to mark "active" in whmcs. yet client is not able to manage his domain. Mostly one has to change name servers, client tried to update name servers from client area but as that cctld is not connected with any registrar so every client contact us to manually update name servers. 

What i am looking for is to have an email notification along with the name servers and the domain name against which he/she was trying to update so that despite a request by client for updating name servers via call or email, we will get the manual action notification via email and our staff can update name servers manually without any physical request by client. (In other words, client may feel that his submitted name servers get updated whatever he was inserted)

I searched through available knowledgebase about this and got a single article on it as https://docs.whmcs.com/Email

I implemented it yet no notification email on updated email address for this module and in client area getting this alert when try to update name servers.

it throws an error as "any-domain.cctld" cannot be managed automatically - please contact support regarding any changes you want to make"

Any help in this regard would be appriciated.