unit returned unrepaired but am being charged

On the 18th of February i took my phone to vodacom menlynn because it wasn't charging,it wasn't going to the internet.They booked the phone and after some time they send me an sms to come en collect it,to my surprise when i got home the phone was still not working.i took the phone back and they booked it after sometime they send me an sms to come fetch the phone and this time the phone came back unrepaired and with a R1500 quatetion.what makes it more frastrating is dat the phone is still under warranty and am still paying for the contract.I have heared people talk about vodacom and their poor service but now am experiencing it.I don't want the same unit and what about all the money i have spend going back and forth seeking help about this phone,am so dissapointed in vodacom and the service they provide to their customers and its frastrating. I really need this matter resolver asap, to even think that i port my number from mtn to vodacom...this really frustrating, I need a new unit and all my expenses compansated back ...I really hope that this time this matter will be attended to by some one who is professional enough to understands my needs as a customer.