Day light ******* by cashier

Hi my name is Phindile Nkombisa I went to Usave Tembisa between 28th or 29th April to buy a few essentials I got there and used my bursary card (intellimali) also asked for a cash back of R300 the cashier processed the payment for the essentials and when she was suppose to give me my cashback she said my card is declining after I got home I checked my transactions online and saw a cashback of R300 and a duplicate of the purchase which was R180×2 I went back to the store the following day and was assisted by a lady Bester (assistant manager) who promised to call me back but didn't until I went back there and they only refunded me R180 and claimed not to know what happened with the R300 then intellimali sent them an email asking them to refund me but to this day they have not and they are not bothering to call me.