We use Stripe for our credit card processing. They provide a secure software and a service to process online payments; they respect and protect privacy, data and personal information. The following information is taken from the Stripe website
Why was a customer’s charge declined?
Since these signals are constantly changing, a previously successful card might be declined in the future. Even if all of the card information is correct, and your customer previously had a successful payment, a future charge can still be declined by a bank’s overzealous fraud systems.
Finding out more information about a specific decline
We show as much information as we receive from your customer’s bank about a decline in your dashboard. Unfortunately most declines are generic, so we don’t have much specific information as to why a charge was declined.
If all of the card information seems correct, it is best to have your customer contact his or her bank, inquire for more information, and ask for future charges to be accepted.