Sony India — Sony Xperia L - Sim slot is not working

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Coimbatore, Tamil Nadu

i have purchased this mobile on September 2013.. one month before that sim was not deducting suddenly. i have given to Sony authorized service center, they are recommend to change the mother board its cost around 7000 rs. i can't pay this much amount for this.. i think this is a manufacturing defect(i have read about from some sites), rest of the all the things is working good condition. please give a proper solution.. i have spend 17000rs for this mobile...i am totally fed up..