Nokia C6
Problem in handset is not solved even after giving it to nokia care thrice

I hav given my handset to nokia care, jhansi rani square, nagpur thrice.. bt still its facing the same problem. they kept my handset with them for more than 15 days and still my problem is not solved. the keys stops working automatically. it has not even been 1 month when i hav got the handset. i request you to kindly look after the matter or get my handset exchanged. thankyou