Horrible service and misled into poor upgrade

I upgraded my contract & phone on 14th June 2015, having being led to believe that the Samsung S6 Edge would meet my needs, particularly with respect to battery life. I specifically asked about this and was unequivocally told that the battery life lasts 1.5 - 2 days with normal use. Upon using the phone, I found the battery life from full charge lasted a maximum of 8-10 hours - and this was without even having my email accounts etc configured on the phone! I turned off various services including GPS, didn't use apps with exception of Whatsapp use, no videos, or camera use or other phone functions. I also turned off any automatic updating and services that require unmonitored network usage - still, the battery life lasted no more than 12 hours! I returned the phone after 3 days as OBF, which they refused to exchange but did acknowledge that the phone behavior was faulty. A week later, I am now told that Vodacom deems the phone to be fine (OBF denied) and I was further told that I cannot change the phone/ contract to one that is fit for purpose! This is absolutely unacceptable practice forcing me to accept an extremely expensive phone/contract which I was clearly misled into.