Am i not allowed to use blank nameservers with my registrar ?

My registrar displaying ads from own pre-configured nameservers.

[Future]

As the question states, we have several hundreds of domains registered with example.com registrar..
Out of same few are registered over years ago.. (where we did not configured any nameservers)..
Without our knowledge and information.. registrar added/pointed those domains to custom nameservers (not owned by us)..

We never authorized/allowed registrar to do so.. We have received several promotional calls directly from registrar informing about there new products and stuff... but never about this cheating..

There are several hundreds of domains.. which registrar denies to change now.. in there support tickets... (they want us to do the same..). They never had issues to change those several 100s of blank domain names to custom nameservers in past !

Is some rule laid down by ICANN ? (to not allow blank nameservers)
OR
Registrar following bad practice ?

[bill]

I've never used a registrar that allowed blank name-servers. That would likely be a misconfiguration of the domain. It is the registrar's responsibility to provide an NS Record when you register a domain. If you don't provide a name server then they provide one for you. That's pretty common practice.

Nameservers don't show ads. Your domains are being parked. Have them turn of domain parking or redirect the domains somewhere instead.

[creeking]

make your own nameservers and use them with your domains

[creeking]

fwiw, I see that dynadot has an option of "no nameservers".

[Imbahost]

Blank nameservers? A Domain requires nameservers, that field cannot be blank.