Refund denied

Good day I purchased R300 cell c aitime from Cosmo city shoprite and tried to load it to no avail because am aware of the no refund policy on the slip I contacted cell c and was told the voucher I entered was invalid so I went back to the store to ask for another voucher only to meet a rude manager who blamed the cashier and refused to come to solve the problem the cashier was crying and begging and it was indeed a terrible experience for me as a customer till date I have not been called to get my airtime or at lease a refund for my money because the manger eventually confirmed it was an invalid voucher I am so angry because the customer service is poor shoprite I want my money bac****!!