Repair of Samsung tablet

On the 06 June 2014, I have upgraded my contract. In October 2014 it was booked in at the service center for a faulty battery. In January 2015 it was booked in again for the battery that is not charging. In August 2015 the tablet was booked in again for the battery that is not charging. This is now the third time that the tablet is booked in for the same problem and their are just fixing it every time. They refuse to replace the device with a new one and to me fixing it every time is not worth it. On the 28 August 2015, I went to the repair center to pick up my device when they check on the system everything was not fix that was on the job card and my tablet has been there since the 05 August for a whole month. I am paying for a device that is more in the repair shop than in my hands. I have launch a complaint with Vodacom & with Samsung but not one of the suppliers responded to my complaints. This is unacceptable for paying for something every month and not have any joy for it.