Faulty Samsung S6 not replaced

I upgraded my vodacom contract to a Samsung S6 Edge in April 2015. It worked fine for 2 months when suddenly the battery overheated and afterwards the battery drained very quickly and it started dropping calls. It was taken to vodacom for repairs and went to advanced repair centre and came back still with the same problem. It was taken back to repairs but came back with no fault found. Still has the same problem and doesnt connect to network all the time. The battery has now heated again and i wonder if it is worth it to do the trouble of taking it in again. I feel it has had to be replaced because im paying for a device thay i cant use. I have been a vodacom client for 20 years and have 7 contracts currently and dont get service needed.