Why can't Rebtel accept any of my credit cards?

First, let me say that I've been a Rebtel customer for almost a year, and love it--but this doesn't mean it can't and shouldn't function better in some regards. Payment restriction is one that I assume a lot of users have run into. Rebtel for some reason cannot accept either of my credit cards, even though they work for much more sensitive, and much larger, online purchases all the time. What this means is that a loyal customer like myself cannot use auto recharge, since paypal, my only means of paying that works, isn't an option for auto recharge. And what that means is that if I ever run low on credit while traveling, I might well not be able to add funds to the account, since this is impossible to do in some countries (why?) and an internet connection might not be available. I have asked Rebtel about this, and received the standard reply: they use a high level of security for payment. But so does my bank, so does Amazon.com and Amazon.uk, so do all the other vendors I use the same credit cards with. It is clear that Rebtel uses a deficient system for payment security--and it may well be less safe as a consequence.

I'd like other frustrated users to join this request that Rebtel finds a new and better informed client for its payment system. I know that the response from Rebtel will be the same I've heard before unless they hear from lots of otherwise happy customers that this is unacceptable as well as unnecessary!