First we need to explain how TeamSpeak normally gets taken over "Hacked"
In most cases TeamSpeak is not "Hacked" but instead somebody has logged into your server claiming to be staff that was not and talked another staff member into giving them a rank. To avoid this you should limit the number of staff members that have the ability to give ranks to others and you should never give a rank without knowing for sure who it is. Most times the person trying to "Hack" your TeamSpeak will say that they are on another device and do not have a mic, If you cannot verify them do not give them the rank.
It is also a good idea to back up your server after it is all set up
To back up your server
Log into your client area here: https://vahosting.net/clientarea.php
Click on Services
Click on the service you want to back up
Click on Snapshots and then click on Create
You can also restore Snapshots from here
If your server is taken over "Hacked"
Click on the service you want to restore