Online delivery charge not disclosed

I placed an online order on the 7th October and the delivery charge reflected R0 but i was debited an extra R50 from my credit card for delivery. This charge should have been disclosed when i did my order. I reported it to the complaints line and have not had any feedback. I tested another order online and again the delivery charge does appears as R0 when i check out. How many customers are you fooling into thinking they are getting free delivery. Very dissapointing service.