You can view receipts of your Volatility purchases in the Transactions section of your Account. Click "View Transactions" to bring up a list of previous payment dates. Clicking on a date will display the corresponding receipt.
If you are subscribed to the Backtesting and Charting products, you can view your current usage amounts including the number of backtested strategies and implied volatility charts requested during your current payment period by clicking the "View Current Usage" button.
Update Card Details
You can change the credit card associated with your Volatility subscription by selecting "Update Payment Details" in the "Account Changes" section of your Account. Follow the prompts to enter your new details.