Agree. They could/should do better regarding informing people. But have you tried contacting them and point out that your bank is not part of RG group? Logically, if your deposits go through fine, there shouldn't be any issues with withdrawals (unless bank changes policy in between).
Looks like you got very lousy info from customer service.
from my point of view, before doing such action as rejecting withdraw (blocking my money on their site), they should be
200% 300% sure, that their decision is correct.
again, it is not rocket science to find out, if my bank is part of Raiffeisen Banking Group or not. they pissed me so much, that I didn't even create some stupid tickets. at least bitcoin withdraws are fine. anyway, as mentioned above, I'm done with them..
Send this to support: "Try Airbank instead of RB group. The account to which I asked you to deposit is actually not part of RB group anyway. You guys must have screwed up your data somewhere."
And please keep us posted. Even if you no longer want to withdraw, it might be worth trying just to see what happens as you push Bitstamp to make sense when they (mistakenly, we must assume) aren't making sense.