If you have a membership site with multiple premium memberships then you probably want to offer your members an option to upgrade their account. Upgrading an account is very easy. When a member wishes to upgrade his/her account, all this member has to do is purchase the appropriate premium membership from the “Join Us/Payment” page (you have already configured this page as part of the setup) while he/she is logged into the site as an existing member. The account will get upgraded automatically once the payment is processed.

If you want to add a little bit of flavour to your membership upgrade path then create special payment buttons that are just like the payment button for the normal premium membership but with a discounted price. Then place it on a page that only premium members have access to. Now, your members can make payment using these buttons to upgrade their account at a discounted price. Since this page that contains these buttons can only be viewed by a premium member, an anonymous visitor won’t be able to signup at this special price.