Multiple journal submissions
Within minutes they replied that they have already published, requesting me to pay x money for the publication fee. 


This sounds like Journal A was a predatory publication (i.e., a scam without real peer review), and not actually a reputed journal.  If this is indeed the case, then having a publication withdrawn from them may actually be better for your reputation than actually having published with them.

That said, you shouldn't submit to a second journal until you've already withdrawn from the first.  In the future, follow that procedure and also make sure that you're actually dealing with a reputed journal before you submit!