Setup custom storage quota to users upload file in media library

The plugins you listed are working correctly (at least from my own test with no plugin installed). They may simply not be designed for the use case you want.

These plugins provide upload limits for individual WordPress users on a single WordPress site. The use case is when you have, say, a WordPress forum or social networking site, and you don’t want individual users on the same WordPress site to clog up the entire site.

If your clients are administrators on their own WordPress sites, what’s to stop them from changing the limited, creating new WordPress accounts, or even removing the plugin entirely?

We are hosting our wordpress in cpanel, but default cpanel behavior when we setup a plan is share the disk space of plan with files and e-mails accounts.

That’s because you’re using the “wrong” account type. A cPanel account is meant for one hosting client, not something meant for you to resell to multiple hosting clients.

Aside from the sharing of disk space, every WordPress administrator on ANY of the WordPress sites you set up on this single cPanel account will be able to access ALL the files under the cPanel account, including the WordPress configuration files and databases of ALL the sites. They don’t need to know the cPanel password to do this. This is a highly insecure way to host websites for different clients.

You need a cPanel Reseller account for this. You, the hosting provider, will have access to cPanel’s administrative counterpart (WHM or Web Host Manager)… from where you can create individual cPanel accounts with the appropriate storage limits for your individual hosting clients.

Alternatively, you could setup one WordPress Multisite Network, and create different WordPress for your clients. This way, you, the Multisite Network Super Administrator, can configure the storage limits for individual WordPress sites. Just note that Multisite has a steeper learning curve and higher administrative burden than a stand-alone single WordPress site.

Good luck!