Bad service

I went to spar tops Jubilee on the 31 March and purchased some staff using my wife card and they said transaction did not go through cos of network, then we went back and made another parchase only to find out that the 1st transaction went through as well and they said she must bring the bank statement to show the transaction and they promised to refund us but every time we go there is either the cashier is not there or the manager or the issue is with head office... Can someone capable solve this please..