Vodacom Will Not Replace Faulty Phone

In early April 2015 I upgraded my contract and handset to a Sony Xperia Z3 Compact. Within three weeks I realised that the phone is faulty. Every single person I speak to has echo / feedback on their end of the call, and cannot converse. I contacted Sony and they gave me a software \fix"that did not work. I contacted Vodacom and they told me to send it in for repair. I handed the phone in at the Umhlanga branch and got it back 10 days later"