10days old fone being sent in for a second repair

I purchased a phone from jet chatsworth centre and after 3 days it started heating up that I could not even be on a call for 5 min.I took the phone back to jet and it was exchanged,I started to use the phone and after 10 days it started to heat up I took it back to the store for the 3rd time it was sent in for repairs and I picked it up on the 11th March,the next day the phone was heating up again.it was doing the same thing! I contacted jet 4 times,no 1 has responded I even left my number for the manager to contact me but she has not.Today (14th March) I had to call the store twice for the manager to contact me,and she told me she can't do much about it.I even emailed Vodacom yesterday, no one has responded I am extremely disgusted and disappointed with VODACOM AND JET.,THEIR SERVICE IS PATHETIC .FOR A 10 DAYS OLD PHONE TO BE GOING IN FOR A SECOND REPAIR,IT IS NONSENSE!