Why i can't get refund ?

Hello my friends,

I sent 4 mails to sales@nextdns.io (2 mails) and billing@nextdns.io (2 mails) but i couldn't get any reply from them. I highlighted my mail address, invoice date, service price, credit card number and invoice pdf form etc... on mail. What i have to do to get refund  ?

I sent 2 mails on 13 June and i sent today another 2 mails.

Best Regards,

Good days, good works...