If there is a fee set on a group tier level, you can override it for an individual user by setting up a fee with the same name as the group tier level fee. The lower level user fee will override the group tier level fee. Read more about override and additive fees.
You can set up a fee on a user as follows:
Go to the Users list. Locate the user you wish to set a fee on and click them.
The user Details page will display. On that page, navigate to the horizontal submenu “Accounts” next to Details.
Find the account you want to set the fee on. Choose on which currency you want this fee to apply. Hover over the ellipsis menu (`...`) for the currency you want to set the fee on and select “Settings”.
Click “Fees” on the vertical left submenu. From here you can add a fee in the same way you would add one to a group tier.