The hostname selected when purchasing the VPS is simply a name associated with the service.
It is usually chosen to be an easy identifier and most likely resembles a fully qualified domain name, such as vps1.example.com
Changing it can only be done by one of our staff members, so please open a ticket if you require it.
This is the name that appears in your client panel and it does not affect the VPS's actual internal hostname.
Internal VPS hostname
As you are the only person with access to your virtual server, you are the only one who can change the internal hostname.
How to do this will depend on the Linux distribution installed.
In most cases you can do it using the command sudo hostnamectl set-hostname new-hostname and editing /etc/hostname and /etc/hosts files.
