Worst service ever!

Pick n pay in wynberg has by far the worst service ive ever came accross! The funny thing is that this has happened more than once, I got to the store right before 1:30 I literally waited for 30 minutes before I could be assisted, there is a long line, 3tills but only one person serving, and whats even worse is that whenever the teller encounters a problem she has to call a supervisor who is at the supermarket and not the actual store, a supervisor that wont even pick up the phone and when customers complain the teller is more aggitated than any of us, does that even make sense???! After waiting so long, I ask the teller to swipe my card for R80 and that I will pay the difference of R7, she swipes a R40 "by mistake" and again we have to wait for another call, eventually the manager comes and assist, not even apologising, and all he says is that unfortunately they cant use the card twice, she made a mistake and I have to find other means of payment, imagine if I didnt have enough money with me which means I wouldve had to leave without my purchase after tolerating so much, half the people walked out fuming but it doesnt even seem like these people care, its frustrating! And then the supervisor tells me im being rude when I express my frustration, ofcourse im gonna be upset like everyone else on the line, if there had been more tellers then there wouldve been less mistakes, because even that one teller was feeling so much pressure with everyone else throwing ugly comments. We chose pick n pay for a reason, and if pick n pay wants to operate, the least they can do is employ people who knows how to do their job!