Upgrade iCloud storage on iCloud account which is not your primary iCloud account

I need to upgrade my iCloud storage for my secondary iCloud account. My primary iCloud account is set as my main iCloud account on both my iPhone & Mac. I have a secondary iCloud account which I use for a business email address. The problem I have is when I click 'Upgrade iCloud storage' it takes me to my primary iCloud account as this is what is listed as the iCloud account on both Iphone & Mac. I have logged into my secondary iCloud account via icloud.com however there is no option to upgrade storage. I can only upgrade storage via settings on either iPhone or Mac however both have my primary account saved as the iCloud account. Anyone know how to solution to this problem? Thank you