According to crt.sh, there was a Let’s Encrypt certificate issued for
voiz.hu as recently as 2019-08-05: https://crt.sh/?q=voiz.hu. And there are Let’s Encrypt certificates for subdomains like
api.voiz.hu being actively issued through today.
If you are in control of
api.voiz.hu and the other subdomains, and want to make sure you are not using Let’s Encrypt in your infrastructure, I would recommend that you replace the certificates on those hostnames with certificates from a different CA, and install a CAA record requesting that Let’s Encrypt not issue for any subdomain of
voiz.hu. You should probably also find any automation you may have running on those subdomains and shut it down.
As far as the main hostname,
voiz.hu, can you tell me what hosting provider you were using on 2019-08-05? Is that the same hosting provider that recently told you they do not issue Let’s Encrypt certificates?