Karbonn Tab — not work properly

Address: Visakhapatnam, Andhra Pradesh

Website: www.korbanmob.com

I porches a korban smart tab in Oct 2012 but the tab not work properly so I give it in korban service centre for check. They return me my tab after 20 day .after some day again tab not working .then again I give it in service centre on 11 march .already 3month completed bt they are not returning my tab . When ever I m asking about tab they say that your tab is in company after some day.
Please do some thing