Removing applied profile

i have a um installation on 5.24 where the users have default profile/limitation of 5gb. once used up they can buy additional data with paypal, this works fine and the new limitation is applied and they can surf again. At the end of the month i need to remove the temporary profile and set them back to the 5gb but the purchased profile remains with the old.
is there a way in scripting of remove profiles/limitations against a user account?
Thx