Samsung S6 Edge still not working

I bought a Samsung S6 Edge 3 months ago from Vodacom. The first month I had 4G almost everywhere and clear calls. It then stopped receiving 4G completely, dropped calls, IF a call went through after about 4-5 tries, it stopped transmitting voice after about 10 seconds, internet was unbearably slow if working at all. The battery became so hot I had to switch my phone off. Most of the time it did not get internet connection. Basically the phone became unusable. After calls to the call centre and confirming that my settings were correct (LTE etc.) I eventually manage to check my phone in for repairs. They replaced the battery pack, main board and back glass. I received my phone back and now my fingerprint scanner does not work 'an error has occurred with the fingerprint sensor'. My phone was in for 2 weeks, I get it back and now I have to return it. Is there a possibility of returning my phone and getting a new one? I have to use this phone for 2 years as per contract and having a 'NEW' phone in for repairs twice in 3 months is not on. The service however was friendly but the product is poor.