How many times must I return my Tablet for repairs

I am totally not happy, I have returned the device to Vodacom 4 times and today no one has gotten back to me regarding the complain I laid on Friday. This is causing inconveniences for me because I did not buy the tablet to play games and be on social networks. <br> I bought the tablet to use for my work and honours research, the first time I returned it was within 3 days of purchase. Every time I have to use the tablet for my research and assignments it has a problem with switching on and not charging at all. <br> I am not happy taking the tablet back as I am scared that It will jam again for the 5th time in June during my exams, bear in mind I had to redo my current assignment research since all my collected data is inside that faulty tablet. <br> Vodacom is really causing an inconvenience for me and I am not happy with their service.<br>