Iphone 7 Plus faulty and vodacom do not want to assist within 7 days

<p>I am seriously unhappy with Vodacom. I bought a new 256GB Iphone 7 plus and are experiencing microphone problems (the caller on the other side can't hear me - it does not happen every time and my voice vade and gets louder). I took the phone back after 4 days of purchase. The phone was send in to the technical department and came back as request denied as the phone in their opinion is fine. They did say they did reload all software and if there was a problem it should be sorted. It is now 2 days after I have the phone back and the same problem continues. I went online and found that this is a general problem with apple phones. I feel powerless as I do not know how to proceed as I am sitting with a phone I can't use for business because the client can't hear me properly. Vodacom refuse the resolve my problem.</p>