Worst customer service

If only it was possible to give zero stars. I bought powerbank from this shop and it was R150 more than the one cold at a different shop, and for the same amount I managed to get a wireless one. I bought it a day before I traveled. When I got back I went to the shop for a refund. The sales person with an attitude sent to me to the manager after I asked how come they don’t make us aware of this policy as it’s not written on the slip or anywhere in the shop. I went to find the manager and with arrogance he asked me why didn’t I ask about a refund policy. In which world do customers go around asking about this? May someone please share what other options do I have to get intervention so I can get a refund? I don’t buy electronic appliances a lot and I just want my money back because the package is still sealed so I don’t understand why they’re refusing to give me my money back.