warranty not good enough

I took my phone for repair again on 27/03/2015.<br> <br> Later on I received a small from MTN insurance quoting an amount of R495.37 for the repair. I rejected since the phone is still under warranty. When I enquires at store if it's back I was told MTN need R350 as I have rejected the quote. <br> <br> I don't understand why should I pay for repair as it still under warranty. Now I don't have a phone that I paid R2799.00 on 2013/11/18 with a 24 months warranty, having taken it for repairs more than twice. <br> <br> I have lost hope since I have been complaining about this but no assistance from the store where I purchased it the have been promised to resolve this for some time but nothing happened. <br> <br> Please assist me on this one. <br>