Not getting proper feedback.

Two weeks ago, I went to the Samsung Service Centre, and told them that my tablet is not charging. They said I must buy their original charger of +/-R380 (of which I did). The table was charging, but took long to reach 100%, when it gets to 40% it switches off by itself and the screen flashes even from 100% being full. On the 14th January 2015, I again took my tablet back and told them that there is seriously something wrong with my tablet,and I think that it might be the battery. When I could not get through to Samsung Cpt, I called the Customer service (***) and on their system nothing showed and that according to their records no work was done yet. Later when I called again to Samsung Cpt, I spoke to a Shamiela, and she informed me that the technicians states that there is nothing wrong on the tablet. Yet, deep down in my heart, I know that they are wrong, or are not trying to look in the matter. My suggestion is that it might be in need of a new battery. But I doubt whether I can trust them put in the new battery, because they have such a 'don't-care-attitude;NULL