If this copier is on a network it should have RUI (
http://IPaddressofcopier). If RUI doesn't work make sure it's turned on, check network settings in copier, check connection via crossover cable etc. and if that doesn't work you can try reinstalling firmware using SST. Set up Department ID Management. Make sure the System Administrator code and password is not easy to guess. Set up a different DepID for a customer to use. They have to enter it then press ID before copying. Set a short period for it to return to screen for entering ID if they don't enter anything.
Then bring up RUI and check total for DepID given to customer. Get them to pay then clear code or delete it.
Should be lots of information on how to do this in the user manuals (except for troubleshooting esp. SST suggestion of course).
You ideally would want a copy of the System Administrator DepID and password so that when you service the machine you can access all areas of user mode.