faulty phone received back damaged

upgrade to a S5 mini could not download anything Vodacom shop had to download my apps. i could not upgrade my apps and had to restart my phone to get whattsapp and calls it said subscriber unavailable. i took the phone in they reset my phone but still the same problem. I send my phone in for repairs at the Grove they sent it to Potchefstroom it came back with the same problem and damaged after 2 weeks. I still have to restart my phone to get my messages and still cant download. My contract is not behind with a payment but now i must pay for a phone that is not working as it should. i have now been struggling for 7 months with this phone this is reticules and Vodacom my service provider don't want to do a thing. i have messages the service department i received a mail back the query has been escalated but a week now and no one has called me back or rep**** future on my mail. i need a phone that works thats what i am paying for.