Can't swipe card for under R50 results in cancellation of order

I ordered a pizza and extras online from Debonairs Atlantis today and paid via EFT including a tip which amounted to 137.65. R50 birthday voucher was deducted leaving a total of 87.65. They later phoned me to say that there is a delivery charge of R20 I told her I don't have cash but I could pay by card she told me they only accept a card payment for R50 and over. I then had to cancel my order. This is terrible service from debonaires