It is possible to add additional bandwidth for a month or recurringly for your VPS. It is not possible to do the upgrade from the client area. In order to perform this, you need to contact our billing or support team via email or from the client area and ask to add the additional bandwidth as you wish. The costs for the extra bandwidth can be seen from the image below:
The process does not include any downtime and once the invoice is paid the upgrade will be instant.