Server Upgrades lets customers upgrade their existing server plan without opening a ticket. It adds an Upgrades entry in the client menu and an Upgrades tab on each server page. For each server, it calculates valid higher-tier plans in the same product category (matching the customer's current billing unit/type), shows the price difference, and lets the customer either pick a specific upgrade or use Max Upgrade to jump to the highest available tier.

When an upgrade is purchased, the plugin:

Validates ownership and CSRF (prevents cross-site request forgery).

Computes the upgrade cost as the difference between the customer's current plan price and the target plan price.