vBCredit is a pain in the ass. It's holding up our migration to vB4.x and that's making me crazy. It's also poorly documented and very "quirky."
That being said, kBank does support vB4.x -- but when we tried kBank it was so lousy that it wouldn't even install properly. But, as it's the only option for vB4.x, I'll probably do some more testing with it soon.