No help , no response from payflex. Don't even reply to emails .

I made payments on the 14th for a missed payment even paid the late payment fee .the money was deducted from my capitec bank account but payflex still says I an owing them and now yesterday I got charged again for the second time for late payment fee on the amount already paid for . Iv been trying to reach them, sent them emails,called them but not getting any help or responded to. My account will keep accumulating interest just because they don't want to assist me . Who will be responsible for those extra costs when it's not even my fault. Payflex cab you please assist because this is not fair at all.