Register for, or log in to, My Vodafone.
Click the 'Bills & Payments' subheading. You can download the details fro your current bill by clicking 'Download your bill'.
You'll be given the option to download your details as a CSV file.
You'll see your three most recent bills further down the screen. If you want an earlier bill, click the 'View More' link below them, until you find the bill you need.
You'll be able to download details from your last 24 invoices.
Click the download icon next to the invoice you're interested in to download an itemised CSV copy of your bill.
The file will download, either to your default download location, or chosen folder.