Cashier's bad attitude

I went to the post office to receive a package I bought online. The cashier then tells me I need to pay R24 as it's an international package, I'm like ok I'm going to get the money as I don't have it with me. I come back with my bank card and he tells me he wants cash cause he has already punched in cash on the system. I'm like u know what give me back mu receipt and I'll come back when I have cash, he tells me no, because he has already put the transaction through and tells me to go and find the cash somewhere else. I'm like where cause my atm is not close by he says I should go to a grocery shop and withdraw at the atm, I end up going to another bank's atm cause I don't know how withdrawing at the till works. So I end up incurring bank charges for withdrawing at another bank's atm and paying a cost which I was not aware of. He was not helpful at all he was very rude