Unhelpful, unattentive and rude service

I specifically asked the cashier 3 times whether they sold airtime for Telkom Mobile. She assured me they did so i purchased R100. When i saw it was for Telkom landline i asked for a refund, she said she could not refund me and then told me to come back tomorrow - impossible since i live in Cape Town. The cashier continually insisted that she was in the right because i had asked for Telkom, but I specifically had previously insisted on Telkom MOBILE. She had a bad attitude and refused to apologise or make it right. I lost R100 and left seriously angry. This kind of rude and unattentive service is totally unacceptable.