IE has a tendency to put an extra page onto single-page jobs if they are printed duplex - which would go part way to explaining why you are getting the charge for two pages.
The charging behaviour for the two pages, and what you can do to alter this, will be somewhat dependent on the version of Uniprint you are running (plus what other configuration settings you may already have).
However, in the first instance, you can set the system to not charge for the second (blank) page by altering the following registry entry:
Set 'No Blank Pages' to 1
I hope this helps.