Out of the box failure

Vodacom - I am writing as a last resort, as I am fed up and frustrated at this point. I bought a Samsung S5 mini cash, roughly around 3 weeks ago as I was in need of an immediate phone. It was from the moment I started the phone apparent that it was as an out of box failure on your side. I sent the phone back under the 1 week return and since have been waiting 15 days now for someone to get back to me on when I can collect my new phone... I am in sales so my phone is my breadwinning object. On top of this I was never offered a lend phone and it took me 6 Vodacom trips before my phone was taken in, in the first place... sim swap was done twice.... if this is how you deliver \good service"I would like to change service providers. I cannot even do so as my cash spent on the S5 or credit it feels is being held ransom and I am powerless to do anything about it. ?#?Frustrated"""