Make sure you are logged into the My Verizon account that is registered as the main account owner.
when you get logged in, you will see My Verizon in the thick red bar, hover over that and click on the link in the drop down box that says VIEW BILL.
When that loads, you will see a drop down box with your latest bill in it, click that and you can select what month you want to view. Then click on the Charges By Line tab, and then you can choose the number you want to view and see all minutes, text and data used.
Hope this helps!!
As of September, 2015, they've changed the My Verizon site. I've always been able to get a detailed call log for previous months using the method above, but now, they've changed it. There is a link saying:
"Previous Billing Cycles: View/Analyze"
but when you click on that all you get is the current month's detail sheet.
Even when you pull up a previous bill, it does this; it appears we can't get this data anymore!
UPDATE: I found it now in a slightly different place. "Previous Billing Cycles" is now at the upper right of the page. It appears to kick you out of the Usage screen when you call up a previous bill, but the detailed info is now on the bill page, on the right tab marked Calls and Messages (it used to be "Voice" and a separate "Messaging").