Vodacom Misrepresentation of airtime/data purchase options

I converted some airtime to buy a data bundle for 30 days, 500MB at R63 as advertised, however I received 250 MB with a further 250 MB ("FREE" Night Owl Data to use between 00:00 and 05:00). When I queried with their customer services, I was told that "as per their terms & conditions" this is relevant to that offer, however, I understood that I was purchasing what they offered "500MB data at R63". I am angry because my expectation was for 500MB not 250MB and 250MB night owl. Surely my expectation is that they give me what they advertise for the price they advertise? I am an honest person and all I want is what I believed I would get if I chose that option. If I go to the shop and see an apple marked R5 - I expect to pay R5 and get the whole apple, not half of it for that price because there are "terms and conditions"?