As a returning player, and older gamer, I have seen my account locked twice in 8 days, due to the Credit Card Fraud Prevention system.
While I appreciate the efforts to protect fraudulent credit card use, there has to be a better way to balance fraud protection and legitimate purchases. What I have learned from interacting with Customer Support, is the best way to deal with the situation of having every single purchase potentially flagged by the Fraud Prevention System, is to simply make one large purchase and then wait out the timer (if you wish to utilize Zen purchases for the exchange - which I do personally).
The current system needs the enhancement of being able to address these constant locks; and I hope such a thing is feasible? Because as it stands right now, it punishes legitimate purchases, generates Support Tickets and Live Chat Support sessions with legitimate customers who can only be told that they are stuck...
In my case, and for illustration purposes, last Friday I switched from a Debit Card through steam to a Credit Card, and added $100.00 to Steam and used $50.00 for a Zen purchase. The account was immediately locked - fine. Then today, on Saturday, the block was removed. Based on the wording of the block, I believed that my Credit Card information had been verified and I was now free to make purchases of Zen at my convenience for Exchange activity.
I purchased 500 Zen, with no issue... to test if there would be an issue.
Then I purchased 3000 Zen, with the intention of finishing with a 4500 total Zen purchase; but I was immediately locked?!
It was only after speaking to a Support CSR did I learn that each and every transaction is scanned and there is no 'authentication' of Credit Card information at all (as I understood it).
In the end, while I appreciate the efforts to prevent fraud, I think the system could be better at being more custom tailored to repeat purchasers, who are able and willing to make legitimate purchases in Star Trek Online.