Unreasonably voided warranty for repairs

Regarding my repair for my Vodafone Smart Platinum 7, which is on contract with Vodacom and upgraded in early January 2017. I booked it in for repair under warranty at Cresta a week ago. I got sms's saying it went to Advanced repairs and then today I got a sms saying I should phone Vodacom repair to accept or decline the quote. The problem was that it kept on rebooting on its own more and more and then one morning it just rebooted non stop and froze at the Android start up screen and repeat. The quote for repair was at over R4000, which I'm definitely not going to pay. The warranty is voided because of the pathetic, flimzy, thin glass screen which is cracked at the back since after I had the phone for a month or two. So now I have to sit without a phone, which I'm paying for monthly??? I'm very upset and believe this is unacceptable. I have been with Vodacom for years now and this is the service I get? I will definitely take my business elsewhere. You just lost a loyal customer.