********** resubmission of a reversed payment

I purchased an item on the 24th of december 2017 using my debit card,I then returned the item on the 26th and I was advised that the money will be refunded into the account that I used for payment.Days passed and there was no money coming into my account I then did a manual debit order reversal with my bank attaching the returned item slip the money was the reversed to my account.To my suprise I get a notification on the 9th of january to say the money went off my account again ,I never went near the shop again who authorised this transaction again and how can they bank the same transaction twice.I went to the southgate branch on saturday with my bank statement as they had told me to do so telephonically only to be told to leave my bank statement as there is nothing they can do their lines are not working.The lady advised me that she will call on monday,she didnt,only now Im called and told that everything is balancing as there are 3 transactions,njani?transaction 1 I bought the item,transaction 2 I returned the item,transaction 3 it went off again without my consent