There are two ways to get to the quota modification page for an account.
Login to WHM.
Go to Account Information.
Click on List Accounts.
Pick out which row in the table represents the account whose quota you wish to change, then scroll right.
On hovering over the row, you will get edit icons that appear beneath a number of options. Click the one under Quota to edit this account’s disk quota.
In Quota Modification, enter a new value, in megabytes. Or, use unlimited that will change from 4Gb to 3Gb. Click change. Now your new quota has been set.
Click Save.
The second way to get to the quota page of an account, click Quota Modification under Account Functions.
Select from the list the domain name or user belonging to the account, then submit the page. You'll be taken to the same page you saw earlier.
If you have a problem getting quotas to work on your accounts, then disk quotas have probably not been set up correctly on your system.