I don't see what all the discussion is about... If you agreed to pay somebody to do a certain job a certain way and they aren't, then you should stop paying them. Demote, lower the pay etc. tell them " I was paying you $18/hr, but the work you are doing is only worth $15/hr, so that's what you'll get paid from now on.
Honestly, I would fire them. They have demonstrated poor work ethic and an unwillingness to learn to do it right, so find someone else who IS willing to work hard and do the job right.
Better yet, just print off this thread and leave it on their desk/workstation. [Coffee]
