Bad service from Debonairs online and Debonairs Alex - Johannesburg

I ordered a Pizza online to be prepared and delivered from Debonair's at Alex - Johannesburg. AFTER PAYING ONLINE I received a call from someone supposedly from the shop to inform me that they were going to charge me R15 delivery fee - I must pay that money when I receive my order. Why was that not mentioned on the order so that one considers delivery charges when ordering online. Now I have to to ask people to give me R15 as that is the whole reason I ordered online - I don't have cash and besides, why are there additional costs after the fact? After one has paid?