Do I interject with actual finance knowledge... hmmm...
Click: You do realize that Verotel isn't a billing solution based in the United States, right? Your bank probably flagged that company as a precautionary measure, especially if you don't make many overseas transactions. But who knows, maybe your bank is one of those Religious Freedom firms that judge you silently rather than provide you neutral service.
Clearing card blocks for Fraud or suspicious transactions usually entail "Did you authorize this transaction?", not "And what was the nature of your purchase?" Porn providers as a general rule don't put "THIS CHARGE WAS FOR PORN" on credit statements for many reasons.
As for not accepting gift cards, it is likely that Verotel, being outside the U.S., has blocked certain BINs as a risk item. I don't know how detailed BIN registries get on the type of cards that are accepted or denied, but you can always look up your card at BINBase and get some insight.
The real questions I have are what's keeping you from one of those nice, private credit cards like I have where you don't have to deal with any of that. I am not really interested in the answer nor is it any of my business, but "I buy prepaid cards for porn subscriptions" is telling of something a bit more interesting about you than about the billing company.
