You can use a Service item for the Statement charge, linked to income, for the Time to charge. If that is Gross, and you want to give them clarity of an adjustment, you can use an Other Charge type item linked to one income account that will run Contra- (negative) and put negative qty, and your rate, to get an Negative on their balance= the offset.
Now your Sales reporting will show Positive as Gross, and Adjusted negatives, such as Sales By Customer Summary with Columns by Item Type. You also can run reports on the Other Charge item, to see info on it, such as Sales by Item. And lastly, the P&L will show two income accounts:
Gross Sales
Adjusted Sales <== contra account