In order to upgrade your VPS follow these steps.
Steps
Login to the Clients Area;
At the left menu, select the “My Services > VPS” tab;
Find desirable VPS and press the “Manage” button;
On the left side find the button “Upgrade” and press it;
Select package and billing cycle you want to change to;
Press on the “Continue” button;
To end the upgrade press “Submit” and invoices will be issued.
Another way
Login to the Clients Area;
At the left menu, select the “My Services > VPS” tab;
Find desirable VPS and press the “Manage” button;
Under Details, you will see Specs, there is red button Upgrade:
Attention #1: The billing cycle dropdown menu shows full prices. The difference you will need to pay will be calculated only after pressing “Continue” (6th step above).
Attention #2: The upgrade is done automatically after the order is received. During the upgrade, the VPS is rebooted from the node side. VPS configuration or its data is not affected or deleted.