... they are taking money off peoples credit card with out permissions ????
Dropbox can't charge you unless you (or someone) has given them your credit card information. If they've been given your credit card information, they've been given permission. If you haven't given them your credit card, then the question you should be asking is "Who did?" and you should be contacting your bank.
If you visit the Support page while you're NOT signed in to a Dropbox account, including these forums, you'll see an option for billing issues. Best to use an Incognito/private browsing window to make sure you're not signed in.