Discovery bank nonsense

I woke up to a negative balances on my Discovery bank account and the reason I was given is that a previous pick n pay transaction from the month of April is only being banked now in June no warning no confirmation from my bank and checking on my statement that payment was done and cleared within that 7 days I am given the run around that I must ask Pick n pay I am not happy with this I need answers now it does not make any sense that it would take almost 2 months for a payment to clear again and deduct from my account again