Vodacom Repairs bad service

My Samsung S7 battery was swolen so I took it to a Vodacom chats to repair. They repaired it and I payed R600.00, after 2weeks the battery is swolen again so I go back and he replaces battery again. Another 2 weeks pass and the phone keeps on switching off by itself so I take it to Vodacom repairs. They gave me a quote for a new battery and back cover again and I payed R 2700.00. Then after 1 week the phone goes off again, so I go back to Vodacom repairs and she called me after I left and said there is nothing wrong with the phone it is on now so I went back to collect. Today again the phone just goes off so I take it back to Vodacom repairs where the lady at repairs told me that the battery should not go that low untill the phone switches off. No that is the reason for my phone not working?? Then she said no they will send me a quote for a battery so I told her but this Vodacom already replaced the battery not more than a month ago. Then she said that there is no guarantee on the battery they replaced because another Vodacom replaced the battery before them. This in completely unacceptable. If they have told me that there will be no guarantee I would not have payed R 2700 to fix the phone. Vodacom is wasting my money and time. This is horrible service.