VODACOM: Pay for 10Gig, they give you 1.8gig

Played Vodacom's 'Unlock Summer' promotion. Won a prize, a free ice cream cone from Hungry Lion. Below the price is 'add on' upsize deals. Offer to me was 10 Gig Data, valid for 30 days at 60% discount (R189), which I bought. Vodacom only give been activated. I PAID FOR 10GIG! They ADVERTISED 10GIG. You can buy on their standard pricing 2 Gig valid for 30 days for R149. Why would I pay more to get less? Trying to phone the help line is an exercise in frustration, as Tobi the help bot does not give you an option where you can select: 'did not get what I paid for", only missing data, which he then want to sent you a usage report. Really FRUSTRATED WITH VODACOM. THIS IS PLAIN DISHONEST AND *****ING.