Lenovo A7600

Got a Lenovo tablett there and after 5 mnths it stopped charging.Took it back 28 Des. 2015 and Martin (very helpfull) send it to the supplier (Lenovo S.A ) .Got it back after 2 mnths (end of Feb 2016) but...came back broken...sim card reader now broken.Could not read sim to access internet.Martin send it back again.Got it back Friday (another month ) meanwhile i pay for 1gb data every month that i'm not using because ...no tablettt. And then but...... see now that the screen display brightness dim and bright on it's own . Then dull (dim) then suddenly BRIGHT again. I can't afford to take it back AGAIN for another month .