Lg mobiles
Handset Problem not been able to solved

I have purchased LG KF 510 handset and there was a problem in my handset from the 3rd 4th month.

the problem was it suddenly gets restart and after restart it shows "no sim card inserted".

for this problem i have visited the service center for more than 15 times but the problem is not solved permanently. it was solved for a small duration and after sometimes it comes again.

once i have given a replacement for that handset but the replaced handset is also having the same problem.

even now m having the same problem but now i cant get free service for the issue which was there from the guarantee period.

Now what should i do?