Motorola L6 MOBILE
They cheat me return my mobile without repairing

I have problem with my mobile L6, which was automatically restart sometimes. i give it to motorola service centre at ahmedabad on c.g. road. but they return my mobile after reseting the software, then after few days same problem create but right now they told that your mobile have problem due to weting in water.

i am 100% sure that my mobile was not wet. but after giving them the gurantee period of my mobile is over. so what i have to do?