Consumer Redressal

I AM PRASANTO ROY ,I HAD PURCHASED A MICROMAX A11 LAST YEAR JUNE 2014 FROM RELIANCE DIGITAL.BUT AFTER 1 WEEK I FACED TECHNICAL FAULT IN IT.EVERY 2DAY AFTER IT AUTOMATICALLY TOOK RESTART WHILE I WAS ON CALL.I WENT TO MICROMAX CENTER (PEARL SYSTEM,MADHYAMGRAM)3 TO 4 TIMES,EVERY TIME THEY FORMATED MY MOBILE AND RETURNED TO ME.BUT THE PROBLEM WAS NOT SOLVE.ON MARCH 2015 AGAIN I WENT TO SERVICE CENTER WITH SAME PROBLEM AND THEY KEPT MY MOBILE AND RETURNED ME AFTER 1MONTH.THEY TOLD ME THAT MY MOBILE MOTHER BORD WAS CHANGED,FOR THAT MY MOBILE IMEI NUMBER WAS CHANGED.BUT THE PROBLEM WAS NOT SOLVE AGAIN I FACING SAME AUTO RESTART PROBLEM.NOW I NEED HELP,PLEASE HELP ME TO GET OUT OF THIS PROBLEM.