How to prevent bogus credit card charges

As of approx. 8pm last evening someone started accessing one of our jotforms and repeatedly charged $5 about 90 different times.  I didn't think someone could have a successful charge if there wasn't a name and/address.  We checked with PayPal and the charges seem to have gone through.  Our accounting office is working with PayPal to get the charges credited back.

I have 2 questions:

1) How can we prevent this type of thing happening in the future?  I want to re-enable this form but I don't want this issue to occur again.  

2) I had a message in jotform that we had reached our payment submission limit.  Can we get these 90 bogus payments removed from our account so that we can still use jotform for payments?

This uses to happen when phishers test stolen cards, this is not an issue related to JotForm only since they will test the card on different sites to see if the payment info is valid. We already protect our payment integrations, but if they are using valid credit card numbers the payments will simply go through. 

A good way to avoid them to spam your form is to add a verification method, you may ask for verification through phone number or email address, if all the submissions were sent from the same IP address you may also provide us with that so we can block them on our end. 

Here is the link where you will find our currently available verification widgets: https://widgets.jotform.com/category/verification 

This guide will help you adding it to your form: https://www.jotform.com/help/252-How-to-Add-a-Widget-to-Your-Form 

Regarding your payments limit, I have reset the counter and enabled the payment form again. 

Thanks.