HOW can You CHARGE ME R50 EXTRA?when YOUR to blame

I changed My banking Details on the 28/12/2015. This people at the counter confirmed That It will deduct from my new account as the debit order will only go off on the 04/01/2016. on the 01/01/2016 my debit order returned unpaid from my old account. I went to Zone Fitness on Sunday 03/01/2016 and they said no the debit order will go off on the 04/01/2016 up to today nothing has gone off from my new account new I had to pay R50 extra and held liable for debit order that was not processed correctly by YOUR ACCOUNTS PEOPLE???*** I DEMAND A REFUND OR I WILL TAKE YOU TO COURT. I WENT BACK TO THE GYM TODAY THEN THEY ADVISED ME THAT THE DEBIT ORDER WAS SUBMITTED ON THE 22ND ALREADY?***??? i GET PAID AT THE END OF THE MONTH AND MY CONTRACTUAL D/O DATE IS THE 1ST..SO YOU BREACHED MY CONTRACT..PLEASE EXPLAIN TO ME *** DO I NEED TO PAY R50 EXTRA..SOLVE THIS OR I MOVE TO A GYM WITH A MORE FUNCTIONAL ACCOUNTS DEPARTMENT!!!DISGUSTED BY THIS GYM