Unprofessional staff and no terms and conditions displayed

I was at the golden highway Lenasia south Pep store at around 12;45 on 18/02/2023 to do an exchange on an item I had previously bought while in the queue I noticed on my till slip that I could do a CASH BACK. When I got to the till point I asked the cashier to do a cashback with my exchange, The cashier didn't even have a name tag on.I asked for her name and she said her name was Nombulelo then she told me that you can only get a cashback if the items bought were R100 and above bear in mind that my till slip doesn't mention that as a condition and it's not written anywhere near the till. I have done a cashback at the store before and I have never heard of that before. I requested to see the manager/supervisor on the floor and a very rude Lady by the name of Thandeka come and said she has just punched out and that there is nothing she can do then she left, and she didn't even greet me. I then asked Nombulele to call the manager who is supposed to take over after Thandeka and she said He/she was not available they had gone out, I was then told to call the head office with my own Airtime because they are not gonna assist me. The manager is not there and that is that. My question is why wasn't it written and why couldn't the manager who was there assist me and call head office and how is it possible that there is no one to take over after one has left