Cell C passing the buck

After 3 calls (many since, plus mails/Twitter/ Facebook messages) Cell C says that due to a Nokia 6 software glitch all my Cell C contract airtime has been depleted and I have exceeded my call limit, because Cell C has been billing me for my FREE 1000 wi-fi call minutes. Cell C advised me to contact Nokia since Nokia did not inform Cell C of the software changes which resulted in my wi-fi calling being inoperable since the last software update (1 May). Nokia disagrees. I cannot make calls. I am the buck that is being passed.