dissatisfaction and lying by service provider

i have taken in my phone for third time with the same issue. I was contacted and told that the device had been exchanged and ready for collection. To my dismay i found that it was exactly the same device i brought in and none of the problems with it had been addressed but vodacom insists that its a new device...same phone,with same scratches/wear and tear except that they had now atrached a different IMEI number to the device and insisting that its a new phone. There is no transparency as to what the situation is and why the phone is being given to me as a new handset wheras it is still the faulty device i took in for repairs.