Warranty Assesment on my Galagy Tablet

I took out a Galaxy tablet with MTN. The tablet started giving me problems in the third month. I have to keep the tablet on charge or else it will loose its power. I took the tablet into the Vincent Park Branch in East London and was advised they will send it away for a warranty assessment. I was advised it will take three weeks. Every time I phone to ask if the tablet is ready, they say they will phone me back, but nothing of the sort. That Tablet is still under warranty and I think I must get a new tablet. I'm still paying for something I don't have and cant use properly. It has been 5 weeks now and I am still waiting for the tablet or someone to advise me on the status of the tablet..