"Biller usage - Invoice details " means you will be receiving detailed billing with your invoice.. This will show you phone calls u have made, how many minutes and other little things a normal invoice doesn't show you.
As for Network Features, this is something u need to contact Rogers Business solutions and ask them. It could be that you are receiving a few network things others dont..
Although some plans may include similar features, they can still be separate plans with different monthly service fees, as well as different pay per use rates for such features as MMS, SMS, etc.
The best thing to do is contact the business department at 1 866 727-2141, and they can review all the details of your plan with you so you are familiar with how it works, along with the charges associated with overages.