Shoprite 100% recycled bag *****

I bought a 100% Recycled shopping bag at shoprite Kimberley , on the bag it states that if you reuse the bag then i will get 50c off my purchase , i gave the cashier to scan the barcode for the discount but it came out Return bag R0.00 , which is very dissatisfying , please update the system or give me my R3 back because i bought it with that intention. Stop misleading customers.