According to Torrentfreak, Swedish payment provider Payson cut access to anonymizing services after being ordered to do so by the credit card companies.
VPN provider iPredator is one of the affected customers and Peter Sunde, the founder, who also founded Pirate Bay, said it is considering legal action.
It appears that the credit card companies are targeting VPNs which are linked to P2P piracy. It follows similar action from Paypal.
Payson confirmed that it was complying with an urgent requirement from Visa and Mastercard to stop accepting payments for VPN services.
Sunde does not believe that the move is to do with piracy, but might be an effort to prevent the public from covering their tracks online and preventing government spying.
US companies are forcing non-American companies to stop people protesting privacy encroachments and being anonymous, and so the NSA can spy even more, he pointed out.
iPredator has plenty of other payment options, but he thinks it is an outrage that Mastercard and Visa have apparently decided to ban a perfectly legal technology.
Anonine, Mullvad, VPNTunnel, Privatvpn and several others are also using Payson's services and Sund thinks they will all join in any legal action.