samsung tablet fault product

I have received a Samsung tablet as a birthday gift last year September, i used it for like 2months time, then it started to give problem, the tablet started restarting automatically, and show battery full when it's on charger, the moment i take it off charger, it shows low battery and starts restarting itself. Unfortunately the person who bought me this tablet cannot find the receipt of purchase since he was busy moving. So i took it to a normal cell repair shop, i thought must not be a complicated issue because it's still like new. However, i have spent about thousand Rand for changing the new battery, reinstalling the software etc., nothing helped. The tablet is still with the repair shop now. <br> I seriously consider this tablet as a fault product, because the problem started after i used it for a very short period of time, and during this short period of time, i did not use it often, most time just lying on the table. This is totally unacceptable, this tablet was a quiet new model on the market at the time i received it, by the time that if i ever can get it fixed, it will be one of the old models, this is such a waste of money.