Hello!
I fear you might have a problem as it sounds, that might not be solveable as easily or by the help of a coder.
Do you have any access on the server, like per FTP or to the database directly? If you have, please let me know and I can see what is doable. If not, and you don't have superadmin access to it's backend either or something else, it seems you would have to go other ways, like as example through a court to gain what you paid for or to request your money back.
Any other attempts to gain access to the server could be seen as a hacking attempt and I would advise against them.
If you have any questions, please don't hesitate to contact me.
My best regards,
Dimitrios Karvounari