Charged unnecessary!

I have a store account with Ackerman's I have a running debit order which goes of on the 20th every month so for the month of November I noticed that the debit order had taken but according to my statement I'm charged for an unpaid debit order R25 I went to the store to try and phone their call centre I was told by the supervisor I can't phone inside the store I must call with my own phone the customer care number on the till slip. So I phoned the call centre with my Airtym and told the person I spoke to about my problem, he then said he can see that the mistake might have been on their side but I need to send my bank statement to them to rectify. I told him I can't query a R25 charge then print out a R25 statement and on top phone with my Airtym. I seriously don't understand why I must suffer for their mistakes.