Want to buy more iCloud storage but DON'T want to join iCloud+.

I understand iCloud storage can be increased by buying a 50-GB data plan OR joining iCloud+. I want to buy more iCloud storage but I don't want to join iCloud+. Online it says this is possible. On my iPad I go to Settings/ My name/ iCloud/ Manage account storage/ Upgrade for 99 cents/ Click block for the 50 GB plan. Nothing happens. Only 2 options show: Join iCloud+ & Not now. I don't want to join iCloud+ so I Click Not Now which throws me back to settings info. How do I buy more iCloud storage without also joining iCloud+? Am I Forced to join iCloud+ in order to buy more iCloud storage space?