Refund of the duplicated payment

Yesterday I went to checkers in Nicolway to do small grocery, I used a bank debit card to pay for the items that I bought, the cashier that was assisting me used the first speed point and she said the speed point its not working then she took another speed point and the process went through, when I was one my way home I receive cell phone banking report and I noticed on my balance that they have duplicated the payment on my bank account, I went back to the shop and the lady that assisted me said that this usually happens to other customers as well but its going to bounce back to my bank account within few minutes and I was fine with that. the money didn't bounce back within the time that I was promised by the lady from checkers. I phoned and asked to speak to the manager. The guy was very rude he couldn't even listen to my side of the story(he was just arguing with me),he even dropped me with the phone.Then I phoned today and asked to speak to the senior manager he couldn't help me as well(he argued with saying that I'm abusing his staff). I was not treated well I'm really disappointed . can somebody assist me cause I want my money that's all I want.