If you are unable to log into your billing account due to not being able to remember the password you can reset it here: https://www.beastnode.com/portal/pwreset.php
Note that the security answer (and username/passwords to accounts in general) is case-sensitive.
If you cannot remember the security answer either please submit a support ticket here - https://www.beastnode.com/portal/submitticket.php?step=2&deptid=2 - requesting a password reset and confirmation of the security answer, making sure to provide as much information from the account as possible for security purposes such as the Full Name, Email Address, Billing Address, Phone Number and/or any order/service/invoice ID #s that you know of.
MultiCraft Account/Control Panel
Your log in details for MultiCraft are different to those for your billing account and were emailed out on purchase (make sure to check junk/spam too for the Minecraft Server Information email if you missed this). The username is your email address by default, but the password will be a randomly generated one by default.
If you forget this you can reset the password here: http://mc.beastnode.com/index.php?r=site/requestResetPw