iPhone upgrade - phone faulty

I upgraded my contract with Vodacom on the 15th of January 2016 to the iPhone 6S with Telecteo Tygervalley. I realized on the 16th that I couldn't hear anyone when they phoned. I went back to Telectro on Monday, 18th, it was identified as an IBF. I was really upset that my phone wasn't replaced, but had to be sent to Vodacom - the fault must surely lie with Vodacom. Today there is still no answer - I want my phone replaced. I'm leaving for East London tomorrow to take part in the 70.3 race - something I trained for 6 months and now I don't have a decent phone for pics or communication.