Here are instructions for uninstalling Matrixrate:
We accept no responsibility for errors; make a backup if unsure.
Matrixrate has been fully stable since Feb 2009, with over 12000 downloads to date. As such we don't offer personalised support. We suggest you look at the docs and examples which should get you started.
You can also purchase the Premium Matrixrate which has more advanced features and a level of free support.