Bad Service from Vodacom and faulty Samsung Galaxy

So, the following happened: I pre-ordered the Samsung Galaxy Flip phone online in August. First installment was deducted on 254th August - keeping in mind I had not received the phone yet! I eventually received the phone end of August. Could not use the phone the first two weeks as you don;t get a charger with the phone - I had to wait on that to be delivered. Eventually got to use the phone - a week after receipt. Called in on the 14th day (you have 14 days in which to return the phone if you;re not happy with it) to advise of an overheating problem with the brand spanking new Samsung Galaxy Flip phone. I was advised to take it into the nearest store. I thought I was getting a new phone - right? NO! They took it and sent it away - for repairs! I called them on 19th September - spoke to the nicest Customer Service Manager - Siya - who helped me so much and advised if the problem persists, I must call him and he will personally assist me further. So I received the call today - 29th September - advising my device can be collected. I switched it on and guess what????? It's still overheating! Then I tried to cal Siya - nobody knows Siya - Customer Service Manager. Was put through to After Sales Service - who then advised they will send someone to collect the phone.

My question is this: 1. Why have I paid TWICE for a faulty device I used for +- 1 week? 2. Why was this not resolved the first time I called it in? 3. Why was I not offered a new device when I called in the first time.