First of all you should check the product pricing page and choose the plan that best suits your needs:
Pricing per Core
Customers migrating from “Classic” per server plans should be aware that newer plans are priced on a per-core basis.
Once you’ve selected a plan, please contact support. We will then update your account and let you know once your plan has been upgraded.
Please note, this is a one-way process. Once your account has been updated it will not be possible to move back to the old pricing.