Debit orders wrongly deducted

In December Bonitas offer my debit order on the 15th while we only get salaries on the 24th and it was refused. When I first saw it on the 28th of December I paid it in via EFT immediately. That same evening they withdraw the full contribution again. Since then I sent many emails to recover my money, at first only to get a new query number each day. Then they sent a mail that the money will be paid back to me, but so far nothing happens. Any further questions only lead to more query numbers. This is January, a difficult month for most. I really need that money back