Game stores lack of training among cashiers

Hi i was at Games Stores in Pinetown Pine Crest Centre earlier today. i purchased a bike for my son along with an itunes voucher. i asked the cashier who was assisting me make sure the voucher was active. he then called his supervisor for assistance and she advised the credits we purchased were loaded on the card. she assured us the card was activated. we then left the store and got into an uber that was waiting for us outside the centre. upon loading the voucher on my iphone i was presented with an error saying the voucher is inactive. We went back into the store to try and get it resolved and presented our original till slip and found that no one is the store knows how to load credits on an iphone voucher upon purchasing the card.We had to wait half an hour to find someone who is able to, which they failed.we wanted to leave the store as our uber had been waiting. they resorted to giving us a cash refund.They kept the till slip with with the bike and voucher purchase and refused to return the original till slip. Please have this resolved as soon as possible. anticipating your response.