If anyone can help me... I need to change a dns for a .net domain without the hosting company. I left them because their services and because of that, they told me that I can change the dns myself.

Is your domain name registration through the hosting company (always a BAD idea, just for future reference)? If it is then which hosting company?

If it isn't you need to log into your registrars control panel, and change the DNS to what ever your new host recommends.

-JasonR