This are your words:
Please assign the following IPs for your nameservers:
ns1.domene-sp.si 70.84.130.26
ns2.domene-sp.si 70.84.130.27

Soo I made
ns1.zastonj.net 70.84.130.26
ns2.zastonj.net 70.84.130.27
and zastonj.net is not working
P.S. I have sent support e-mail 15 hours ago!

We've received your email.

We are looking into the problem.

You've made a bad thing. You've defined zastonj.net in its own nameservers

ns1.zastonj.net
ns2.zastonj.net

Would be better to contact your domain name registrar and change your DNS records

to

dns.hostony.com
dns.hostony.org

for domain name zastonj.net

Then you'll ba able to use these nameservers

ns1.zastonj.net
ns2.zastonj.net

for all your clients under your reselle's account.

If you have any questions please let me know.

Thank you for understanding.