Duplicate transaction

I poured petrol on Sunday the 6th of Dec, and when i swiped the machine switched off but the transaction went through as my cellphone notified me, but the guy whjo was assistng me said it got declined (Approval #402632). He then did the second transaction whch also went through and notified me on my cellphone and told me that the first transction will reverse in 24 hours. it is Tuesday now and the money did not get reversed ans when I went to let him know he said I must submit my statement which my bank charges me for it. He even said it is not the first time this is hapening so clearly magement has to resolve this as I will not risk experiencing the same thing and will use another garage going forward.