As far as i know u can transfer money from/to a visa or mastercard to WMZ vallet using WMkeeper classic. At least it was possible two years ago. To do that u have to register a WM account at http://www.wmtransfer.com/eng/ and download a WMkeeper.
It's a pity i cannot tell exactly how can u do that, for i don't use webmoney for two years or so...